Animal kingdom is MY favorite park, and my kids love the lion king show and the boneyard. BUT- its really hard for a three year old to SPOT live animals. We'd spend half the safari ride going "do you see that hippo?" "No". "Do you see the alligator?" "NO". Followed by tears. MGM has playhouse disney, arial, muppets and beauty and the beast, pluse the playground. Not to sound anti-family, but I would choose the park YOU like the best,
There are many more characters available there and he especially loved eating at Pizza Planet. Playhouse Disney, Annimation building, Muppets 3D, Honey I Shrunk the Kids playground, & Little Mermaid were all big hits. 3/4 of day can be spent here on just "young kid" type things.