Hi:
If your kids are into planes then I second Fantasy of Flight. My son, 7 at the time and my husband, went up in a biplane for some real views of Orlando. It was an open cockpit and they had the time of their lives! It even topped the helicopter tour we did the year before!
Gatorland is a half day adventure and on the cheesy side but the kids loved it too!
Kennedy Space Center held my husband and two boy's (10,7) attention from open to close. I skipped it because I was bored there years ago but they can't wait to return. You need to take the bus tour and try out the simulator or so I'm told!
How about Busch Gardens Tampa? We were pleasantly surprised! The kids loved the rollar coasters and all the animals.
Have fun!