When I travelled with toddlers, I made sure there was time for the playgrounds. Each themepark has one. At MK, there's a playground in Toonstown and a small one on Toms Sawyers Island (which, by itself, is a playground for toddlers). In Epcot, there is a nice playground in Norway. At MGM, the Honey I shrunk the Kids has a playground.. although large and hard to keep track of the kids. ANd then, the best I think for toddlers, is the Animal Kingdom Boneyard.
Character breakfasts were great, if they aren't terrified of characters that is. Just walking around is cool. The street shows at Epcot are great for toddlers because YOU DON'T HAVE TO TAKE THEM OUT OF THE STROLLER! This is a huge plus if they're sleeping.. that way you can enjoy the entertainment. At MK, there was Storytime with Belle, which my kids enjoyed (but it can get very hot there.) Taking the boats, monorail and busses were big hits with my toddlers. And if there is time and the weather cooperates, there's the hotel pool. You will have a blast with your toddlers, there is so much to do that they will enjoy.
Enjoy!