Midway is good--- as it's name implies, it's about midway between the east and west coasts. Not to far from Shark Valley which is a great stop. Loop Road is a must drive if you go.
Another option is Collier-Seminole State park. FHU, it's on the west coast side of US 41 near Naples. Just outside the park is Corey Billie's airboat ride. He's a great guy and will give you a good ride. Big Cypress Bend board walk is in the general area and worth a visit. If you want to visit the southern area of the park , we stay at Miami-everglades RV park near Homestead for the FHU and then drive to Flamingo. Stop at everglades alligator farm on the way as well as "Robert is Here" road side fruit stand. ... and if you are that far south, go ahead and drive down thru the keys and if you go all the way toward key West, stay at Bluewater Key RV resort , You won't be disappointed.