A few ideas, depending on your interests and tolerance for heat: (1) Drive out to Key Biscayne, about a 20 minute drive from Miami airport. Enjoy the views from the causeway, and have lunch at the Boaters Grill in Bill Baggs Cape Florida State Park. If it’s not too hot, rent bikes or 4-wheeled surreys for a pedal around the park and visit to the lighthouse. The park does close when it reaches capacity, so if you do go I suggest going on the early side. There are shower facilities if you decide you want to bring swimsuits and enjoy the beautiful beach. Crandon Park is also on Key Biscayne — you can watch cruise ships sail away from the beach if you are there in the late afternoon. (2) Zoo Miami is terrific — count on about an hour drive from the airport but you’ll have plenty of time to get there and back. (3) If you prefer to avoid the heat, Miami has some great museums (such as the Perez Art Museum) and you can walk around Bayfront Park. (4) Lots of fun places to stroll and shop and dine on Miami Beach. Not sure what’s on the program that day (if anything) but the New World Concert Hall is a smallish venue with great performances if you like classical music. (5) If you want to enjoy authentic Cuban food, head to Cafe Versailles on Calle Ocho.
Enjoy your visit to Miami!