Do you have a carrier, like an Ergo, for him? I find I so handy with that age in the parks. If you don't have one, I would get one plenty of time before the trip to get him used to it.
If you can afford a monorail resort, their transportation is so convenient to MK and EPCOT, my kids' favorites.
I'd purchase the Memory Maker photo service. Our youngest had amazing reactions to the characters and the photographers captured some wonderful candid moments that I didn't see from my vantage point when we were in the moment. And actually, that's a great reason to get the photo package...since you have someone else to actually take the photos, you can really stay in the moment with your child and watch his reactions without worrying about looking through the camera.