@Fat Nick Enjoy....go at the little guy's pace.
As with what
@Deranged Hermit said, stroller is a must, but you prob knew that. While they are great at carrying ####, you need to fold them up on the buses. So plan out what you are going to take (diapers, food, change of clothes, etc) and make sure you have a soft bag or something that all of it will fit in. Bc there is nothing worse than standing in front of a bus, with a line of people behind you and trying to stuff baby bottles into your pockets while trying to fold up the stroller.
Have lots of food and snacks on hand to keep him happy. Instead of packing them, there are grocery delivery services that can deliver anything you want directly to the resort and they will be there when you check in. They are great for things like milk, boxes of cheerios (for kids snacks), and bottled water cases. Things that take up a lot of room/weight in checked bags.
If you are eating breakfast at a buffet, be sure to grab some bananas and dry cereal before you go. F it, you paid for it, take it. You never know when a mid-day banana will come in handy.
There are hidden places where the little guy can run around. In the MK b/t big thunder mtn and splash mtn. Also in Epcot, there is a similar inside (air conditioned) playground in the exit to Mission space. These are great places to take him while one of you gets a chance to ride something.
On the subject, take advantage of rider swap. You get a "rider swap pass" at the attraction and one of you gets in line (regular line or FP) The other one goes for ice cream with the kid. When the parent is back, swap the kid, and the other one takes the pass and goes through the FP line to get quick entry into the ride.
On rider swap and FP: I'm sure you have your FP's worked out already, but if you want to modify them, you make a FP for one ride (say big thunder), and wife makes a FP for another ride (say space mtn). Then using the swap pass, you're both get to use the FP lane for those, and it only costs you 1 FP slot.
Don't make a FP for Dumbo b/c here the standby line is actually better. When you get in line, they give you a beeper and you go into the big top tent where the kids can run around and play on things, while you sit and soak up the AC. Then when its your turn, the beeper goes off and you go ride.
Know the locations of the baby care stations. They are indoors and relaxing locations that the baby can sleep in for a bit vs being outside in the noise. Also, they have a bunch of stuff avial for purchase like extra diapers and creams and stuff so you don't need to carry everything with you or panic if you ran out of something.
if I think of more, I'll post. Or if you have questions, just let me know.
Enjoy!!!