On my team, we have about 20 students and 12 mentors. The mentors really try to help the students get involved. Our team is about 50/50 girls to boys. Most of the girls (about 7-8) usually do the more spirit things and awards and essays. The boys are more involved with the building and testing of the robot, but we make decisions with the whole team.
As to scheduling conflicts, my team has our meetings after most sports and activities finish in the day. So football (for example) practice usually ends at 530, and our meetings don't officially start until 6.
This helps us not have too many conflicts with outside activities. It's difficult, because some parents don't like trekking to the school at 9 pm to pick up their child from an activity, but we make it work.
