What to do for my sleepover...?

I want to have a sleepover but I won't be able to have it at my house because my mom won't let me and I can't have it at a hotel because I want to invite a lot of people. I want it to be very mature and sorta like the Blair Waldorf sleepover from Gossip Girl (Season 1). So where should I have it and how should I decorate?