We have 'play biting' issues too with our 14 wk pup Toby, its not aggression its just a puppy thing, some are worse than others. He is more bitey when excited and playing, it just takes time and patience til they understand the limits they can go to and how hard is too hard. Time out is about the only thing that is working for us, no, ouch etc just seems to spur him on, so we put him out the way until he calms down. He is particularly bad with my 6yr old son as he loves to chase him around and nip at his legs/ankles, its (so Ive been told) a normal thing for him to do as he sees my son as his litter mate and when young pups play together they bite each other, when they hurt they yelp and run off, thus then the game stops, but because he doesnt have other pups around to learn this he uses us and my son to learn. He is better now at 14wks than he was at 10 wks and so far no blood has been drawn, but it seriously hurts if he catches us the wrong way or we of course quickly remove our hands/legs from his mouth
I wouldnt worry about having friends around, the more people he meets the better, just if he starts to get a bit over excited, then remove him from the situation so he learns what is acceptable and what isnt.