Ds really enjoys Epcot. Here's a few attractions he loved on our last trip (3-1/2yrs)
Soarin' (The Land Pavilion) (40" height requirement)
Spaceship Earth (slow moving ride but he always wants to do the "Epcot" ride)
The Living Seas - Nemo ride and also Turtle Talk with Crush
Test Track (40" height requirement)
Innoventions has some fun interactive stuff for kids as well
DS also enjoyed both the Mexican Pavilion and the Norway boat rides.
In the World Showcase, each pavilion has a Kidcot station where kids can color on a mask and get a special paper "charm" to hang from it from each country.
There are also character greets through out the park - we saw Snow White, Aladdin, Belle & Beast when we were there. Winnie the Pooh can be found in the British pavilion. They also have a caravan of characters that makes an appearance on a double decker bus a few times a day (check the times guide for location and times) and there is also the character connection spot at Innovations West.
Check your times guides for different entertainment that is going on around the parks. For instance, in Japan there is a candy & origami artist, and the Taiko drummers (ds loved that!). In Morocco there is a band called "MoRoccan" that plays very upbeat Moroccan flavored "rock" music and a dancer that performs. The Chinese pavilion has acrobats that perform. The American Pavilion has the Voices of Liberty. The French Pavilion has a different performers as well - the living statues and an entertaining mime to name a few we've seen there. Anyway - you get the idea...
Hth!