Agreed, the immediate Sea World area is crap for food.
Orlando is stuffed full of chain restaurants, so it's always going to be a drive to find anything unique or even somewhat uncommon.
I-Drive is a mess to drive down most of the time, the traffic is erratic and crazy. So I don't go down there much and can't personally recommend too many places there. The only places I ever eat at on I-Drive are a couple of excellent Indian restaurants, but not all that kid-friendly. It's mostly one big tourist trap, though.
The area around the Bahama Breeze mentioned previously is probably your best bet. There are a handful of decent places over there. There's also some place over there called "Jungle Jim's" that looks very kid-friendly and unique, but I've never been there myself.
Also, down on Sand Lake Road there are some nicer, classier restaurants in the Dr. Phillips area. Some are quite expensive, but there are also some more moderately priced places and some smaller franchises (like Moe's and such) there as well.
You can get there by heading towards West I-4 when leaving Sea World, then staying RIGHT at the big exit fork (don't get on I-4) and RIGHT onto Turkey Lake / Palm Parkway. Take that a mile or two, then turn LEFT onto Sand Lake Road. They're down that way.
=)