There are no camps in the traditional sense for adults. The closest things are weekend fantasy camps; an example of one, the rock music fantasy camp, was illustrated in "Simpsons". Perhaps they have those things for other, more intellectual interests, that the OP's son might like. I would not recommend for him to be a camp counselor. That job requires heavy social skills, especially for older kids. Not a nice job for an 18-year-old aspie, who may even be emotionally younger than the kids he counsels.
I've also been seeing banner ads for "Camp No Counselors", but those are party/alcohol/hook-up getaways, kind of like a booze cruise, but you're in camp. With adult version of cheesy camp games. Hardly something the OP's son would enjoy. Not to mention he's too young to drink. I definitely would, though, but I'm 32, and built up social skills over the years. At age 18, I'd get eaten alive in that environment, alcohol nonewithstanding.