Simply ride the bus/trolley.
LeeTran stops right in front of the park. You can drive your RV in, park and never have to drive again until you're ready to leave beautiful Bonita Springs. If you want to go to Fort Myers Beach, it's an easy two step process: (1) the bus Route 150 from the park to Lovers Key State Park trolley stop (see http://www.rideleetran.com/pdfs/current%20schedules/Route150.pdf and following page), and (2) the trolley Route 400 from there to Fort Myers Beach (see http://www.rideleetran.com/pdfs/11-14-13%20schedules/route%20400.pdf and following page). During the season with the amount of traffic going to Fort Myers Beach, it's the only sane way to go. When you want to come home, it's an easy trolley and bus ride back.