N.P.
do they like anything? Harry Potter, Sims, Facebook, Angry Birds, etc??
Take whatever all three of them like and go from there. It's sad that your son doesn't think he has any friends to invite! Would you want to do something for the 2 girls at your house then do an outing to a movie or bowling or something like that for just your son and one buddy?
I have a daughter that will be 13 in June, and I hope the teens haven't hit your house like mine! I swear she has such an attitude lately! She is more self centered then she ever was as a toddler, lol.