Thaaaaat's a good question. Gym is an obvious choice for activities. A scavenger hunt could help teach new students about the layout of the school too (information that could save your life presented in a fun way?) if we're doing this on/around intros of course. They could always start out in the auditorium for demos, or those could be in the gym too.

I'd think we would probably stick mostly to those areas (other than locations for the scavenger hunt if we do that) and the courtyard (might be good for capture the flag/obstacle course) since they can all hold a lot of people.