I'm not quite sure what you mean. I think the more people at each event is better. Get as many people as you can. Members of the team, friends of team members, parents, siblings, other teachers, administration, etc.
The "minimum" is as many as possible and the optimal is the same.
In the pit however, is an entirely different story. You want 3 or 4 students maximum and 2 or 3 mentors. Anything more than that and no work can be done.
