Not sure how many, could be 4, could be 40. I wanted to hire a big inflatable thing or similar but the other organisers think we should be spending the money on advertising instead (budget is £500, £200 for food, £300 for advertising/entertainment) and doing games/team building stuff instead. Event is a drop in so might get people coming all at once or slowly, a few at a time. All the games I can think of or google suggests will only be fun in a big group or if they know the game already. I am nervous because I work with little ones rather than teenagers. I have teenagers of my own but never entertained a big group of them before.