J.K.
I used to live in the Keys. It's been 18 years since I left, so the restaurants may have changed, but the things to see certainly haven't. The kids will love Key Largo's Pennekamp State Park. Go for a ride on the glass bottom boats. Get down in the V-hull early so the kids are right next to the glass sides. The coral and tropical fish are amazing. Further down the islands, on Windley Key, stop at Theater of the Sea. There is a lot to see there, including dolphin shows. Long Key State Park is terrific for me. It's a good place for the kids to get out of the car and run around. If you are near Big Pine Key at twilight, go for a slow ride around the bay side of the island. That is when the Key deer start moving around. They are white tail deer that have evolved into a dog size because of the lack of nutrition.