I almost skipped my college reunion because I had gained about 40 lbs since I last saw them, but decided not to.. and I'm really glad I went, though it has motivated me to lose and keep it off for the next one.
I'm not going to be one of those people who say "go or you'll regret it forever!" but if you have really good friends who will be there, they'll be happy to see you whatever you weigh.
Flipside - I have skipped my highschool reunion and have no intention of ever going because I don't want to see those people whether I weight 150 or 250