AT Epcot, on the side of spaceship earth (as you face it it is to the right), at night, the concrete tiles have lights in them. They light up and then go away. My son loved "chasing" them when we were leaving Epcot. I wouldn't recommend it right after Illuminations but if you were there prior to that it is fun to watch and little ones really enjoy it.
I agree with Legoland at Downtown Disney. It is a wonderful way to pass a evening. They also have a playground area, etc. The wonderful world of Disney can make things crowded though so keep a close eye on them.