We live in Orlando and have season passes to Disney. Our 2.5 year old LOVES MK, the Mickey Toon Town Fair is closed for good. Now when you walk into the park on the right there is an area where you can meet Cinderella, Sleeping Beauty, and Belle and you can meet Mickey and friends. Then in AdventureLand you can meet Tianna, Ariel, and the faries. We did the Princess lunch in Norway (Epcot) for our daughters second birthday and it was wonderful (soo expensive, but worth it)
Our daughter loves all four Disney parks, we like Sea World , but not much. The customer service there is terrible, and I think it's a little expensive for what it is.
We really don't like Universal, there are very very very few things for kids there. I would wait to go there until kids are teens.
There is a lot to do at all the Disney parks, HS is probably for a little bit older child. There is a disney Jr. show, car stunt show, and little mermaid show that my daughter LOVE. I don't know about the height requirements, but this park has Aerosmith ride and the tower of terror.
Kiddo LOVES animal kingdom. I would suggest MK and AK, if you can only do two. You have to see the Wishes fireworks show at MK and the Epcot fireworks are great as well.
PM me if you have any specific questions, we have been at Disney the past three weekends in a row. :)