S.S.
my son goes for summer camp every summer for 2 weeks. unlike your son he is not with family. I pack him 2weeks worth of clean outfits and an extra 10 pair of underwear and an extra 2 outfits. half of it comes back unused sigh......but if your son is with family they will have washers and dryers he would be fine with 2 weeks worth of clothing. don't over think it. and don't go buy a lot of new clothing. camp is for playclothing. I go to the second hand store and buy a bunch of tshirts and shorts that it won't matter if he does the mud tug of war or the swamp hiking thing. they can just be tossed into the rag bag. good luck