If you are going to Savannah, you might want to stay at
Skidaway Island State Park
http://www.gastateparks.org/SkidawayIsland
I have stayed there at least twice and loved it each time. My last stay was 5 nights of peace and beauty.
You have to drive through downtown Savannah to get to the park. You can make advance reservations, but you get to drive around and choose your site after arrival. It is very shady and wooded with mature trees and huge lots that provide a lot of privacy, electric, water and sometimes cable TV. They rent bicycles too.
My very first campground I stayed in when I started driving my RV in 2010 was at Savannah South KOA . I loved watching the water fowl there, but the lots were small and crowded. Many of the advertised features were not operational when I was there. I stayed one night and have not been back again, but the birds were awesome.
Midway between Charleston and Savannah is Hunting Island State Park east of Beaufort SC. Actually it's 21 miles down highway 21 from Beaufort to Hunting Island. It is my all time favorite place in the whole wide world. The 8 miles of beach are totally unspoiled, the campground is adjacent to the beach. It is well worth the detour to go stay there, even if just for one night, if you can get a reservation. I try to stop by there in the spring and fall. I was just there for 12 nights in April and I've already reserved the max of 14 nights in October. The island makes me homesick for the Caribbean where I lived 23 years.
http://southcarolinaparks.com/huntingisland/introduction.aspx
I've written volumes about the place on my blog. I first went there in 1964 as a mere child and fell hopelessly in love. The state has worked hard to protect the island in it's natural beauty. I think I've been there 7 or 8 times in the past 3 years.
If you go there, be sure to stop at Gay Fish Company on 21 before the island and pick up their fresh off the boat shrimp to take camping. The shrimp is so fresh it cooks super quick, don't overdo it.
Oh and pay attention to the lot sizes when looking over the reservations, they vary widely in parking size due to the plethora of trees. It doesn't matter which lot you end up on, the beach is 30 seconds to 3 minutes away by foot. You can hike a mile or two down the beach to the lighthouse which is open to the public for climbing to the top. The views are awesome. You can also drive there too. Pay attention to the tides, at low tide the beach is super wide, at high tide it's narrow. Campers spread out up and down the beach, so it's never crowded.