Sweet Sixteen Party, What To Do?

A surprise party would be kinda cool, but not cool enough. You could rent a limo, have it take her and her pals to their favorite spots around town, and then drop them off at a hotel for a night. (Marriot, etc.) You could check on them every once and a while. When(if) they order room service have the deliverer bring up the cake, instead of what they ordered. And try to get a suite if you have a lot of people.