John Pennekamp Coral Reef State Park, Key Largo, mile marker 105 (30 miles from wedding),
Tavernier mile marker 95, Islamorada mile marker 75, Fiesta Key Resort KOA mile marker 70 (check www.koa.com for reservations because it was sold to developers and employees expect it to close in three month). Long Key State Park mile marker 65, Curry-Hammock State Park
mile marker 56, is perfect for big rigs and close enough to Key West for day trips. I would not take a big rig into Key West. http://www.floridastateparks.org/FindaPark.cfm
The state parks have water/electric/dump station and their website even gives length of sites.
I would reserve now for March. Do a internet search for rv parks in Islamorada and you will find many. I always check all nearby towns on this website for vrv parks. Remember comments change from year to year as rv parks may change from one year to next. Suni from Texas, wintering in Florida