When mine were toddlers they loved playgrounds/free play areas like MK's in old fantasyland (don't know for sure what is in new fantasyland), Honey I shrunk the kids in DHS, the boneyard in AK.
MK- dumbo, carousel, tomorrow land transit, Winnie the Pooh, railroad
AK - just toddling around, Safari, Lion King held their attention as did flights of wonder
Epcot - fountains (they could sit and watch dancing fountains, or regular fountains all day! ) nemo, figment, spaceship earth, all of the seas, the acrobats in China
DHS - not much really - muppets was ok, honey I shrunk the kids, mine were afraid of the witch in the mermaid show. They did like the Disney Jr show.