I was born and raised in Va. and spent 50 of my 66 years there.
You will get freezing weather/snow in Va. until after Easter.
The closer to the coast you go, the warmer it is.
I would take a gallon jug or two of drinking water and just a few gallons of water for the toilet in the fresh water tank. Throw some pink antifreeze or even cheaper, is windshield washer fluid (it does not freeze) in the gray and black tanks.
Depending on you fresh water tank location, I seriously doubt you will have a tank problem on the trip.
I now live in North East Ga. and still look for freezing weather until
at least March/April.
I would the fill up in Fl.
The lack of weight from full tanks will also help slightly on gas millage.
Hope you have a safe trip.