Ok guru - So, this is your first time and you won't be back any time soon. Initially, you really should stay in the park. There are other housing possibilities outside the Disney grounds, but the experience of staying the park is second to none. With three kids, you have your first choice - spend money on the room or save money on the room because the kids aren't going to care about the differences.Value resorts may be your best bet given the kids. With three young ones you want kid stuff available and you don't want to be in an atmosphere that they don't consider kid friendly. Pop Century is the better value resort there, and there is also the All Star resorts. I find that Pop Century has the better atmosphere for a young one - my son is 5 and has stayed there a bunch of times and loves it. There are several pools to use, some fun hidden stuff like a water splash fountain near the 50's building, and of course the statues of the big Rubik's Cube, bowling pins, Mickey Phone, etc. Just a very kid friendly atmosphere. Also, in the rooms, the wait staff will notice that you have kids and at least one during your stay they will decorate the room window(s) with their toys and washcloth/towel animals. My son loves that kind of stuff.The food there is decent, and better then most of the mid sized places. The bus system is a one stop trip and is closest to Downtown and Epcot. The ride to the Magic Kingdom is a little long, so there may be some impatience but it's not so long that you forgot what you were planning on doing once you get there. The biggest drag, though, is that the Pop bus stops at the parks are always the farthest from the door so the walk at the end of the day sucks. You get used to it, but the kids never do. And three year old will have to be carried several times on the long nights.If you want a nicer room there are obviously a ton of choices. I would suggest though that the room isn't the reason you go there and you can spend your money in a better fashion then getting the room that is $200 a night as opposed to Pop which usually runs in the $50-$85 range (I think, depending on deal).Next, your usual itinerary. Since this is the first time, there are certain things you are going to want to do. But, since you have young ones, there will be things you can't do. I'm going to assume a week trip. 7 days on site. First, plan one of those days to do nothing. Nothing at all. You may end up doing something and that's fine, but don't get reservations or plan a certain thing that day. Make it a go with the flow day - kids can do the pool at the hotel the whole day or whatnot, or you can go to a park. Your call. But having that flexible day with young ones is important.You obviously need to budget most of your time for Magic Kingdom. Generally, plan about 2 full days there. You will want to make sure you hit:1. Small World - all kids.2. Pirates - 3 year old might not like it - dark and there is a small drop of about 7 feet in the water ride. If the 3 year old won't go, one of you can take him to the Camel ride which is near.3. Haunted house - not scary at all but dark. If 3 year old can't do it, there are a lot of things to do in the near vicinity while the others go on.4. Transportation Ticket Authority. A very slow ride through Tomorrowland. All kids should like it. It's a calm down ride. It's just fun enough to not be boring, and you can take a breather while on it.5. Indy cars. Obviously, the 12 year old will love this. 6. Splash Mountain. The biggest drop here is 50 feet so probably not good for the 3 year old. There is a shooting galary close by if not.7. Big Thunder Mountain - fast. But it is a roller coaster.8. Space Mountain - dark and fast, there is an arcade right next to it for anyone that doesn't want to go on.9. Buzz Lightyear - everyone should love.10. Pooh Bear ride. All kids.There are of course other rides, but these are the top ones to make sure you get. Don't try for Dumbo. It always has the longest lines. The flying carpets by the camel are the same ride and the line is always half the size.Then there are the shows. There are 2 that you can't miss. The first is Mickey's Philharmagic. 3-D show with Donald getting a hold of Mickey's Fantasia Sorcerer's hat. The seat in front of you sprays water and air on you during the show. 3 year old might not like it but mine did. The other is Tiki Room. Birds signing. Tiki polls too. Very funny. All should like although there is one dark moment that the 3 year old might balk at.Hidden tip - there is a cool down spot at town hall. There is a small movie theatre type room always playing cartoons, it's air conditioned, and it's a good rest point to take a break. Characters will be right in the front of Main Street for pictures so you won't have to search too far. Finally, Mickey's Toon Town Fair - all young kids usually love it. The rides are simple and fun for the kids. Mickey and Minnie are always at their houses for pictures, and inside the big tent building there are usually either Mickey friends for pictures or the princesses.You aren't going to get to do everything that Magic Kingdom has to offer ride and attraction wise, so don't bother. You will make it a job more then a vaction. The kids will dictate how it goes. If they aren't ready to do anymore rides, see one of the shows, or walk around and do pictures. You can always jump on the train and take a round trip around the park for a fun ride/rest thing. If you are getting parkhopper passes so that you can go between the parks each day (I recommend them) you might want to consider a monorail ride to Epcot, or even to one of the monorail hotels to walk around and see them.EPCOTThe 12 year old will love it here. The must do's you know: Spaceship Earth/Soarin/Mission Space/Nemo Adventure/ Test Track. The lines will be long at all places so plan accordingly.But there are other things to do there that most people miss. The Imaginarium is fun (although it was better 20 years ago) and Figment is still there. The Furutre World aspect of the park also has a lot of places right there that are inside quiet attractions. There is a thing there teaching kids about home fire safety, waste management, etc. They can be fun depending on your kids.Treat Future World as separate from the World Showcase. They are 2 parks in 1 - think of them that way. I would say plan 2 days here as well, but that is because of my love for the World Showcase. You might not need a whole day just there and could therefore blow out EPCOT in a day. All the big rides are in Future World so you will be there a lot. For a quiet sit down a relax ride there is Livin With the Land in the Land Pavilion. Slow boat ride through farm type scenes and then through the aquafarm and fisheries of the Disney scientists. It could very well take you the whole day to do just the Future World stuff. Your 3 year old can't go on Mission Space and TEst Track might be too much as well. Spaceship Earth can be dark, but it's slow and not very scary. Nemo is a blast, but the big shark from the movie is there, so be warned.If you are going to focus time on the World Showcase, then you are in for a treat, as are the kids. Canada has some cool stuff to see, but no ride. England doesn't have a ride either, but there is a toy store. Of course, there are kidcot centers in every country where they can draw a mask and get stamps in their passports (get the passports for them. I've never seen a kid not love those things). After England you take a walk over a brdige to France. Get your wife to take the kids to the bakery while you go talk to the French women in the stores. Pretend your buying something for her.While your on that side of the park, food, treats and whatnot abound. Each country has something fun and different. All have stores. All have some form of food. Most have alcohol and other drinks. The rides are in Norway (boat ride with a small 25 foot drop backwards that your 3 year old might hate) Mexico (slow boat ride while watching a 3 Caballeros movie (donald and his bird friends) which is very fun, and there is the Great American Adventure movie in the America pavaillion. Great show. Very very very loud.If that kind of thing isn't your cup of tea then you can do the whole showcase in 2 hours and be done. Or you could lost there. StudiosThere is a ton to do here and again, you won't get to do it all. Just about ever ride there is a must do for most people - Aerosmith Rockin Rollar Coaster, Tower of Terror, Star Tours, Indiana Jones show, and on and on. All the rides for the most part are loud, fast and fun. There are smaller kid oriented things as well, but we find that if your young one doesn't love loud noises and fast moving things that they won't love this park that much - but the 12 year old will love it. You may end up spending that extra day you didn't use at EPCOT here. Basically, between the two its what the kids like.Animal KingdomIf your kids love animals you'll be here for a full day. There is a small kid ride area that they all should like and there are older kid stuff like Everest, Kali River Rapids and the Jungle Safari. If they don't like animals this park can get boring quickly.Water parks - you will be going to them if you go in the summer. They are water parks, so nothing special to report. I would consider going to them in the afteroon if you aren't doing a full day because they are usually more crowded in the morning.Downtown Disney - a very small kiddie area ride area is here, but besides that it's shopping. The lego store is cool though, as is the biggest Mickey store on the planet. You will have to spend at least 1/2 a day here because you're married. But it's fun.Eating - your choices are so numerous it's hard to pinpoint anything. Each hotel has a place to eat and the parks have tons of them. Some suggestions.Get a least 2 or 3 character meals if you can. There are many many choices. Crystal Palace in MK is Pooh and friends. Chef Mickey's in the Contemporary Hotel is buffet style with Mickey and his friends (Minnie, Donald, Goofy, Pluto). Goofy's Liberty Tree Tavern is very good American food family style (all you can eat at your table, tureky, ham, roast beef, mac and cheese, mashed potatoes, etc) Goofy, Minnie and Chip and Dale are there.The castle has the princesses there but it is nearly impossble to get in and it's really not for boys.At Epcot, the Land has a sit down place that is family style with Chip and Dale, Mickey, Minnie and Pluto. The aquarium has a sit down place where you can sit by the glass tank and see the fish, but no characters. The Polynisian hotel has a character breakfast buffet and the best diner you will find on the planet. Seriously - get dinner reservations there and thank me later.MGM has a few character places as well that are buffet style.You don't HAVE to have reservations all the time, but almost all of the time you do. They leave space for walk in's and they try to never turn anyone away.As you can see - you will not get everything in. Don't try. Just enjoy yourself. A rough plan might be something like this...... Let's assume you stay at Pop Century.Day 1. Check in in the morning. Get the kids acquianted with the hotel in the morning. Have lunch. Hit MK in the afternoon - it will be cooler and less crowded. Go down Mainstreet to Tomorrowland and hit the Indycars, TTA and Pooh Bear Rides. If there isn't a long long ride, you can also hit the Buzz ride. If you have a diner reservation for, say, the Crystal Palace, make your way over there, around the back of the park and hit Small World or Peter Pan. Have your meal. Afterwards, go over to Frontierland and check out the lines for Pirates, Flying Carpets, and that area. Once it starts pushing the 7:00pm time you are going to want to start finding a spot for the parade and fireworks - if you are doing them. Just about anywhere works, although I recommend some place on Main Street facing the castle for the best view of the fireworks. You can save seats while groups of you go through the stores there and get snacks. The place across from the Liberty Tree has awesome ice cream cookie sandwiches. The fireworks are over late, so you make your way out and back for a good first day.++++ If there are extra magic hours anywhere, that is the best time to go to those parks and hit the most popular rides. Plan with and around them if you can ++++Day two you will probably want to wake up early and get breakfast at Pop. Hope the bus to MGM and spend the day there. Maybe a character lunch. The fireworks and laser show there starts late as well. Mickey battles all the Disney bad guys so be warned with the 3 year old. Of course, if a whole day out is too much, I suggest going back to your room around 2 or 3, and letting the kids hit the pool until dinner time when you can either stay at Pop or go somewhere else for the meal and night time fun.Day 3 - hit EPCOT. If half day, then half day and take the monorail over the MK for the rest of the day. If full day, get dinner reservations at Italy or Japan or Mexico. Day 4 - rest day. Dont' plan or reserve anything and let the chips fall.Day 5 - MK again. Do the stuff you missed on day 1/2. IF you do a 1/2 day here and then the rest of the day at Animal Kindgom that's a full day.Day 6 - water park. If whole day you're set, if half day, go back to your room around 2ish. I would suggest this is the good day for dinner at the Polynesian at Ohana. Honey Corriander wings, teryaki dumplings, steak, chicken, pork, sausage, potatoes, shrimp, and bread pudding covered with ice cream and Banana's Foster Carmel sauce. Seriously. Don't miss this meal.Day 7 - last day. Depending on your departure, hit the park you had the most fun at. Do one or two things. Enjoy yourself. It's the last day.Don't be afraid to spend time at the hotel instead of standing in line for an hour to do Pirates. If you go in knowing you won't get everything done you will enjoy it more. And make sure that you and your wife pick sometehing that you want to do. It's your vacation too. It is almost impossible for the kids to not have fun there, but it can become hard with one kid - I can't imagine 3.Some helpful tips - Get a double stroller if you don't have one to bring. You will be amazed at how much the 8 year old sleeps or rests in the thing with the 3 year old - and it holds a lot of stuff. Also, since you are staying at the park when you buy something have it sent to your room. Less to carry. Think about getting a photo guide for a day. It isn't cheap but you can get all your pictures done by someone else for a day. If you don't do that - use and abuse Photopass. We've had hundreds of pictures taken with those things. You can't beat them.With 7 days, 21 meals, reserve about 10-14 meals. But know that you won't hit them all. The kids are going to act up, be too tired or not want to go. Give yourself that many choices knowing you won't get them all in. And don't forget to take in all the little extra stuff all over the place that a lot of people miss. Pictures at great spots. Little snack stands with something a little different. A face painting stand for the kids. A character here and there that aren't in the wide open. Explore. Have fun. Take the whole place in, not just the rides that have 45 minute lines.And don't forget that the hotels have things to do as well. Check out the boardwalk and those places. Take the boat ride from MK to Wilderness Lodge just for fun, or the boat ride from MGM to Downtown. Whatever. Do that stuff. It's a blast.If you need specific info let me know. Good luck.