For Memphis I would stay at
Tom Sawyer's RV Park in West Memphis, right on the Mississippi River and very relaxing. For Percy Priest try to stay in site 41 of the Seven Points COE - all of the lakefront sites are nice but 41 is huge and very nice - of course, once the six months window opens you will need to be online to nab one of them, especially on a weekend! I assume you will be staying at Anchor Down in Dandridge.
Virginia is going to be a bit out of your way. Little Creek is a nice military park in Virginia Beach. In Savannah, Skidaway Island State Park is one of our favorites though
Creek Fire RV Resort is also very nice. You should also enjoy Pelican Bay at Mayport if you can get in. Jacksonville doesn't have a lot of choices though
Pecan Park right off I-95 just north of the airport and there is also
Flamingo Lake is a few miles west of Jax just off I-295. Stagecoach in St. Augustine is also a good choice - a good distance from the beach but very close to the outlet shopping centers.
It sounds like a very nice trip - just make sure you get your reservations as soon as possible!