Hillary:
If your son meets the minimum height requirements for Test Track and Soarin' at 40" in height, I say go. Not only will your children enjoy Nemo and Universe of Energy with its dinosaurs but they'll have fun taking the time to explore
Innoventions--a children's museum of sorts. Don't miss Sum of All Thrills where you can build your own plane or snowmobile and then ride it in a simulator. (There is a height requirement there, too, but if he can't ride, he'll love Storm Struck. It's still my 10-year-old's favorite.) Take the time to explore the "games" in the room where you exit Spaceship Earth, also.
Check out Coca-Cola's Cool Zone and test all of their soft drinks for free before you head over to World Showcase or sign up for
Agent P's World Showcase Adventure on your way. Stop at Canada's
Kidcot Fun Stop to collect a "passport" that can be decorated at each country while they get a stamp or signature. It will keep them focused and allow you to shop and go at the pace both of you need. The Canadian pavilion now includes a lumberjack show and the Chinese acrobats are a "must-do." Epcot is not just about rides but experiences, and for those who keep that in mind, it can provide quite a memorable one. Consider snacking your way through the countries instead of sitting down for lunch, and you add another layer of fun.
Your recollection of Coral Reef is the same as mine: good food with a captivating aquarium for my children. Make a 6:30 p.m. reservation here and then you'll have enough time to find a place to catch Illuminations to end the day.
Wishing y'all a magical vacation.
Whitney