There are two sections to Edisto Beach State Park. The Ocean side campground is the best with the ocean breezes, but the marsh side campground is an easy bicycle ride from the beach.
It's South Carolina in the summer, so there are mosquitoes. And the raccoons are pretty fierce so you want to make sure your food is stored securely, so you don't wake up to critters eating your potato chips.
The restrooms and showers are clean.
Edisto Island is one of the least developed islands in South Carolina. There is a Piggly Wiggly grocery store to pick up all the things you may have forgotten. There is an ice cream shop and several restaurants, but it is pretty quiet. My favorite thing about staying at Edisto Beach State Park is bicycling to the beach, bicycling along the paths in the state park that lead to a shell mound, built by Native Americans around 2,000 B.C., and bicycling for beers at one of the little bars overlooking the ocean. Another plus is the park's proximity to Botany Bay.