Have you considered universal Studios? With the addition of Shrek and Jimmy Nutron, it is a great place to take young kids. Before the additions my DD preferred IOA over any other place (including any WDW park).
Now she loves US. It also has Curious George, Fivial and Barney play areas, the Barney Show and Woody woodpecker Roller coaster. Oh I can't forget ET.
There is so much for kids ot do at IOA. Seuss Landing is amazing. It is so well done. there are several rides there for hte kids. IOA also has Flying Unicorn, Toon Lagoon and the Jurassic Park play area. DD also likes Storm Force
Sea World is great too, but it is more "touring" than anything else. The shows are good and will keep kids entertained.The 2 rides are Thrill rides and the 4 yr old would be too young.