For the water parks, I would suggest that if you are spending a couple of days in the Disney Parks that you add the WPFAM option to your tickets. This would get you into one or both waterparks, and into DisneyQuest as well for a pretty reasonable price. I have a feeling your boys might like to spend an evening playing at DQ, perhaps while you get your shoppin' on at DTD. (Okay that was sexist, for all I know you could be the video game queen)
We have never done the airboat tour, only the St Johns River boat tour out of Blue Springs State Park. It was amazing, but I would suggest you wait until a winter trip for that as the manatee overwinter in the Springs, and are not to be missed.
My tip would be to get the Unofficial Guide - Beyond Disney. They have a fairly good section on the various airboat outfits and which are the best. It is a short enough section that you can grab a Starbucks and a comfy chair at Chapters if you don't want to buy the whole book.
Our local library has it too, but it is a couple versions old and the UG books are updated frequently.