Divide groups in appropriate size. For example a group of 20 be divided into 2 groups. A group of 24 be divided into 4 groups. Each group, now teams, should line up facing in the same direction.
Like the game of Tag, the person who is IT must tag other people. When those people are tagged, they link with the tagger and team up to tag others. No one is left out of the game.
Instructor claps or makes a noise and the participants has to get into groups based on how many noises were made. For example, There is a group of 20 participants and the instructor claps 6 times.
Operating Parks and Recreation programs without volunteers would be next to impossible. Currently I utilize 10-200 volunteers on a project but quickly discover that they are very difficult to retain.