Driving down to Key West is a unique experience, water to the right, water to the left, a 7 mile long bridge ... Some nice state parks.
We drove down to the Everglades (in through Homestead). It really is an all day trip. Just a little way past the main entrance, is the Ahinga Trail - LOTS of wildlife - including alligators! Turtles, lot of different types of birds. There are many other trails between there and Flamingo. At Flamingo there are more trails, but they have two different "excursions" - I would do the "Backwater boat tour" - Very interesting. The other one is the "Florida Bay Tour" - we did not like it as well. Down at Flamingo there are BOTH Alligators and Crocodiles (one of the few places in the world where their habitats overlap).
Closer to Miami is Shark Valley in the Everglades. We took the tram tour and really enjoyed it. Saw a lot of alligators, turtles, birds and would do this again. It is a shorter day than going to Flamingo.