The Atsion ranger station is on the highway. You pull in the driveway right from 206. It's a dirt parking lot but any car would be able to pull in.

I'm not familiar with the Mullica Hill trail- I've ben on the Mullica River trail, perhaps you mean that? Either way, none of the trails in Wharton are paved, I would expect it is sand, most likely occasionally it'll actually meet up with a sandroad and you'll walk on that for a bit. None of the trails in Wharton that I've been on are super well blazed, so keep that in mind, but they are usually still easy to follow. The terrain in Wharton is very very mild so I would expect a pretty easy hike- but expect to travel a bit slower than usual since you'll probably be walking on sand. Since I'm not sure what trail you mean, I cannot recommend a starting point. I've only camped at Godfrey and Batona, so not sure what Mullica River campground would be like (I assume you mean Mullica River campground because as far as I can tell there is no Mullica Hill campground besides a Quaker Friends School summer camp). If it's like the rest of Wharton you should be able to swim in the river. I would recommend researching the route in to the campground for your car ahead of time if you only have 2 wheel drive. Frequently to get to the campgrounds in Wharton you'll have to drive down sandroads that are sometimes soft and deep. I do it in rental cars, usually without problem.