Ultimate Frisbee is a great option for a fun, hassle-free activity. It requires minimum adult involvement and can provide hours of fun for the youth group. Also, those who are not as athletically inclined can usually learn to throw and catch a frisbee fairly quickly so there is more involvement among the teens.
The rules are simple. Two teams, two goals (a soccer or football field works well), and a frisbee are all that are required. One team begins by a "throw-off" (similar to a kick-off in football). The frisbee is then passed from team member to team member up the field, but when a team member has the frisbee he or she cannot run. They must keep one foot planted and pass the frisbee to an open member. A goal is scored when the frisbee is passed and successfully caught inside the goal line. The opposing team must try to knock the frisbee out of the air (no physical contact is allowed). If the frisbee falls to the ground whether it was knocked down or simply not caught, it is turned over to the other team and they work their way to their goal. Another throw-off is only required upon scoring.
If you have a large park or sports field, try this for a summer evening of fun with your teens. I guarantee they will LOVE it!