Just starting research. I'm looking at November and one day to do Flamingo Marina, then over to South Naples via Shark Valley for a couple of days. Maybe kayak around SandFly Island and a manatee boat tour? Is Sanibel Island worth a day or some inshore fishing in the area? Not really particular about that, just getting out on the water for whatever is in season at the time.

For Biscayne, looks like too late to snorkel and possible weather issues. Maybe kayak in the mangroves?

We went during the government shutdown in Jan 2019 so not everything was open and available.

Key Biscane we just did a boat tour...they took us out to thr light house on Boca Chita Key where a bunch of yachts were parked to "camp". Beautiful but not very exciting.

Everglades we walked the Anhinga Trail and saw 8 ro 9 gators and then went down to the Flamingo Visitor Center and saw some manatees and a salt water crocodile. We also did an airboat tour, which was awesome - we did a private one - I think it was twice as long as the non-private one and went further out into the swamp - saw tons of gators.

(obviously, luck, weather, and seasonality will play into what you do and don't see)