Taking my kid for his 5th birthday, just doing a long weekend though. Will be doing two park days, not too worried about a meltdown. He's an...interesting kid. Fascinated with dangerous weather and natural disasters. Guessing he isn't old enough to appreciate Universal, so my immediate thought for one is Epcot but no clue on the other. Any suggestions from the peanut gallery? Price isn't an issue. We are not staying on site. One of my friends lives nearby, so we are staying in his spare bedroom and using their extra car on park days.
Kinda tough question ...it really varies interest to interest.
IMO, Epoct with a 5 year old would not be my 1st choice.
If you/he has never been before, then you must do the magic kingdom. Its the flagship park, and hands down has the most attractions and entertainment for him at that age
After that, I would recommend the Disney Studios for the 2nd day. If he like anything on Disney Jr, then thats the place for him. They have the most TV and recent Movie characters there —Big Hero 6, Jake, Oso, Handy Many, Doc mcStuffins, Toy Story, Monsters U...etc. He my recognize them quicker then some of the older ones. Do a late lunch at Hollywood and vine where he can see most of them right there. Plus you have Toy Story Mania (a must) Star tours, Indy Jones Stunt show, Muppets, Dis Jr show, Frozen (if he's into that) and Jedi Academy (sign him up early for that if interested)
Animal kingdom is a close 2nd there...If he is really into animals, I'd say go there, but Studios wins by a nose hair.
Why not Epcot? 1/2 of Epcot is the world showcase, which in itself is amazing, but not sure through the eyes of a 5 year old. You said hes an "interesting kid" so if that involves learning about other countries, then by all means go. I'm not knocking it, there is real amazing things and people to learn from there, but I rank that as part of a longer, multi-day experience.
Outside of that, you do have some good rides, but not sure of his tolerances..Test Track, Soarin, are the bigger ones. Space Ship earth is nice, Turtle Talk is fun, and Energy Adventure is slow and could be boring (45 mins long and only part of it is with cool dinosaurs)
Back to Studios and Animal Kingdom. Both of them can be done by 5-6pm easily. As a matter of fact, a lot of the characters are done by 5 and if you dont want to sit around waiting for Fantastic, can I suggest a fun excursion? And i'm assuming you are not getting a park hopper ticket.
Go get diner reservations at Chef Mickeys at the contemporary. Afterward, book the Pirates and Pals Cruise that launches right from that resort. Its a cocktail hour type party with dessert and such, pictures with Capt hook and Smee then followed by a boat ride out to the center of the lake to watch the MK fireworks...they pipe the music into the boat.. The boat pirate 'Patch' is a fun guy who sings songs with the kids, does trivia and each kid gets a small prize. Back at dock you are 'surprised' by Peter Pan.
Or...if you already seen the MK fireworks....and money isnt an option. Charter a pontoon boat from the Beach club to go over to Epcot and watch illuminations from the lake. Very cool experience. It might be a nice way to bring the friends you are staying with. No park ticket needed. If you go to Disboards.com, there are people looking to split the cost of the boat, so you can save money there. Afterward, spend a few hours on the Boardwalk enjoying that atmosphere.
Enjoy!!