5 days ain’t gonna get ‘ya to Tampa/Orlando, but you can make a rush to Pensacola (as mentioned) and maybe to Topsail SP in Sandestin (Henderson SP in Destin will be filled w/ snowbirds).
Mississippi will give some of the best and longest stretches of waterfront/white expansive beach roadside views of any of the states.
Ocean Springs is a nice National cg just beyond new Hwy 90 Biloxi Bridge.
You MUST go to Dauphin Island and walk dogs on the beach at the Cg also next to a historic fort, a gulfarium (not my thing), an’ a bird sanctuary you also can stroll. $50, but take the ferry across Mobile bay to Gulf Shores and on to FL.
But before all that…
In Texas, head to Corpus, get on north Padre, see Port Aransas, camp on Gulf, proceed to Fort Goliad SP for Cinquo de Mayo Battle site and stroll Goliad town square. There are RV spots along Port Lavaca, Placious (I want to see this spot based on an YV.net tip a few years back). Brazos Bend SP is an hour from MD Anderson and is practically in suburbs of Houston. Watch for gators (not in Dec.)
Galveston and ferry to coastal backroads into LA. Lake Charles has Jeff Davis SP in north end of town. Shoot down to Holly Beach, camp and crab on the beach. Take coastal scenic drive and stay in Palmetto SP south of Abbeville (our newest SP, and sans mosquitos in winter). Get some Steens Cane Syrup in Abbeville, and some boudin and seafood, and talk to a cajun, chere..
Grand Isle SP takes you too long – it is a Gulf Coast fishing village and hurricane target.
Fountainbleu SP puts you on the North Shore of Lake Ponchartrain. One hour across causeway and $100/nite letrs you RV camp IN the French Quarter.