So the guidance counselor started by allowing my kids to choose their own groups. I had a minor freak out because I have to plan all my group work lessons based on who can and can't work with whom. But whatever, it was her funeral. She gave the groups of 3-4 kids 6 plastic solo cups and a rubber band with 4 pieces of yarn tied to it. They had to work together to use the rubber band to stack the cups in a pyramid without touching them with their hands. Here are some pictures:
This group only had 3 so the boys took turns controlling two strings at a time.