Ideas for a 17th Birthday in NYC?!?

I'm turning seventeen and would like to plan something for my seventeenth birthday; It's with about twenty or so other people and it can't be expensive. I want somewhere fun, maybe a nice restaurant then somewhere to go after?? I've already been to comedy clubs and karaoke bars, and Lips seems too pricey.. and suggestions?? I can probably find a restaurant, I'm more concerned with the "somewhere to go after" part..