Haven’t been in ages, but the Cheeca Lodge in Islamorada was one of our favorite places to stay. You should still be able to see The African Queen in Key Largo. There’s a place we used to like in Key West that was situated on the water with lots of turtles, fish and young sharks around the walkways. I cannot remember the name of it and my google searches are failing me, but keep an eye/ear out. Mallory Square Sunset celebration in Key West can also be fun. I also recall dining at Key West’s Pier House which was nice. While north of Miami, in Dania Beach, Jaxson’s Ice Cream is always a hit. Lester’s Diner is also good…although we usually hit the Fort Lauderdale location.
If you go over to the Everglades, there are lots of airboat options. The actual national park also offers a slow moving “train” sort of experience. Snorkeling/scuba, sailing, and fishing are also really good activities with plentiful options if they interest you. I’m not a huge glass bottom boat fan, but it’s also worth it if you don’t want to be in the water.