21st Birthday in Vegas :) this september!!?

My 3 girlfriends and I are going to Vegas in September - I'm the last one to turn 21, so we're all Vegas newbies (at least with gambling, drinking, and clubbing). Any recommendations - especially specific to this September - for four girls our age would be great! Dining, gambling (we are completely inexperienced.... how do we start?), clubs, comedy shows, or other activities? We're staying at the Venetian - and for right now we have dinner reservations for Bradley Ogden's restaurant and Sushi Samba, but we could always change them!