I would say over three is ok, But older than 5 would be better.
At USF there is Woody Woodpeckers Kidzone. There you have Fivels playland and Curious Georges Play area. Both great play areas. You also have Barney's Show and of course ET. There is also the Hanna Barbera Ride which is excellent and the Woody Wood Pecker coaster.
At IOA there are three play areas. One is by the Bilge Raft Barges, the other is in Jurassic Park and the other on Suezz Island. The Cat in the Hat is a great Dark ride and there is one fish two fish, sort of like Dumbo with a twist. There is also the Suess o Cell a Carosel. Two newer rides at IOA are Storm Force ( Disco Teacups) and the Flight of the Unicorn a kiddie Coaster.
Both of these areas will entertain your smaller thrill seekers for a good period of time.
Hope this Helps