I went to lots, and had a few for birthdays.
Apart from one of them, we were all members of the same cadet unit. Usual group of us was two couples plus two other friends. The two couples usually did have a bit of a mess around, and everyone had the odd drink (maybe one / two beers or alcopops), but generally it was chatting, bitching about other cadet units
, a bit of singing to the theme tunes we gathered over our adventures, a few card games and eating junk food. We never caused any trouble, always tidied up the following morning, replaced any supplies we had used up, etc.
I'll make my decision when DS is that age, but, as several people have said, if he will be drinking (and I'm not foolish enough to think that by just not providing him with booze means he won't drink) or having sex, I would rather have it going on in my house, where I know he is safe, and where all the group are safe, than going on the middle of a park somewhere.
Not all of what I got up to at 16 was ideal, but generally I was hard working, successful and committed to my school work. If DS is the same, and his friends are, then I will probably be fine with it. When they happened at my parents house, the lads were upstairs in my bedroom, whilst us girls were in the front room (there were more of us). At my friends, the two couples tended to room in together, with the other two friends in the spare room. I think I may well do the same as my parents, but again, will have to make that decision at the time.