I'll assume you're talking the actual Everglades National park. Maybe I'm wrong, there are plenty of places north of the park that offer swamp tours, air boat rides etc. As far as the national park you have the Shark Valley entrance off US-41, Tamiami Trail. The main entrance is near Homestead. There are several private campgrounds in Key Largo, less than 30 miles from Homestead. There are a couple of parks in Homestead, I wouldn't recommend them. Miami Everglades RV park is 8 miles north of Homestead so access to the park at Shark Valley or the main entrance are both around 30 minutes away. We happen to be there now. Nice park, large round pool, walking path and other amenities.
There are tours of the park at Shark Valley and a number of places along Tamiami Trail that offer airboat tours. Not much else along Tammiami Trail except some Indian villages. Big Cypress National Preserve runs along the north side of Tamiami Trail, Everglades Park to the south.