Fort McAllister State Historic Park Campground is off the same exit as the KOA (which the in-laws tell us is very nice), about ten minutes’ drive east, two turns. Follow the signs. Not difficult to get to and worth the extra miles.
The big drawback: no reservations, first-come/first-served, which means that a phone call just as you are in range of the place (say a half hour or less) or a drop-by off-season (very late fall, winter, and very early spring) might get you one of the fine sites in the mile-loop. Most campsites are pull-throughs with a combination of packed sand and grass… ok for big rigs, but best for anything under 30 or so feet. They only have two-way hookups, with a dump station conveniently located on the right at the end of the one-way loop (as you exit). The campground has an excellent nature trail (about a mile long) and you’re at the end of a peninsula, looking out at the salt marsh. You can apparently rent canoes and kayaks, and there’s a free boat ramp. There are a couple of fishing tables, too, if that’s your gig. It was really nice just to walk around after driving all day. Oh yeah–free cable at GA State Parks! None of the sites has a much better view than the others, so go for the biggest, most private (an exterior of the circle) sites. The views are restricted by the green growth on the perimeter of the island. You can walk out to the marsh’s edge from your site, at most sites, and birdwatch. Bring your Petersons.
Additionally, the bathhouse was very clean, the staff is dedicated and friendly, the park is an environmental gem, and, last but definitely not least, there’s a civil war fort with “mud walls” (interesting construction method) that was attacked successfully. We were there in December when they had some re-enactors, and it was exciting to walk down the mile or so (you could easily drive and easily find parking) from the campground and watch them (more southerners than yankees, of course) march around and shoot off their cannons. Cheap State park prices, too (it might have been 20 a night).