gee, am suprised no one answered your post, so what happened?
It's a tough one, I would base my decision on my childs ability to handle responsibility. Do you trust him? and do you trust his friends?
My child is only 14, so I can't compare with a situation of my own, but I identify completely with you being the fuddy duddy, I have exactly the same problem as it seems my rules are always stricter than the rules set By her friends parents.
Having grown up with many beer swilling pot smoking friends and having parents who were clear about the trust they had in me I never fell for the peer pressure thing. My desire to maintain my parents trust was stronger. I only hope I can raise my own child with that same desire.
Hope it went well.