There's so much to do in central Florida beyond the parks.
Consider a nighttime bio-luminescent kayak tour near Merritt Island (we used
A Day Away Kayak Tours and loved this). There are several companies in that area. Use insect repellent. It was so worth going out there!
Try the sensation of Skydiving... indoors.
iFly Orlando is at 8969 International Drive in Orlando. We've never tried it... yet.
k1 Speed has indoor go-carts at 5228 Vanguard in Orlando, not far from International Drive and Municipal Drive. Sounds fun on a rainy day.
We've also enjoyed seeing the manatees at
Blue Spring State Park in Orange City, a little north of Orlando. There's a nice walking trail, picnic tables, and
concession activities like a nature boat cruise tour, kayak/canoe rentals, and a guided Segway tour. Lovely nature park - it's popular so go early in the day. I don't know if they take reservations, since it's a state park.
Can't comment on local airboat operators. We've enjoyed airboat rides down in the Everglades but no knowledge of central Florida's options.