i can't believe I'm the only one to say MK and Disney-MGM Studios. I went last May with a 5 year old and 2 year old. Obviously, MK is a no-brainer, as has already been said.
I thought MGM was great for my 2 year old. Beauty and the Beast, Muppet Vision 3D, Playhouse Disney Live!, Voyage of the Little Mermaid -- my 2 year old loved all of these, as did my 5 year old. My five year old ALSO loved Star Tours. We didn't see any of the shows (Fantasmic, Lights Motor Action) but I'll bet both would have loved them.
As for AK, well, I'm not putting it down, but at least for my two-year-old, I'm not sure she got anything out of it that she doesn't get from the zoos we frequent. Well, she did enjoy Festival of the Lion King, at least before she fell asleep inside. And we didn't go see ITTBAB, so I can't comment on that.
My 5 year old says he enjoyed Dinosaur!, but it also scared him a little, too.
As for Epcot, I can't recall anything she really loved there. MAYBE Journey into Imagination. But as for my 5 year old, I must admit that Test Track was his favorite ride/attraction outside MK. Neither of them seemed to enjoy Turtle Talk with Crush, but I admit that it was one of MY favorite attractions -- the visual technology and the human improv skills, in combination, were outstanding.