Have the youth bring their own towels and have the leaders provide several blocks of ice. Go to a grassy park with hills or somewhere else with grassy hills. Youth take turns sliding down the hills on blocks of ice. Hilariously good game to play on hot summer evenings.
** This is so fun, but forbidden in some areas because of the damage it can do to lawns, so speak with your local parks and recreation deparment before doing it. — Jenny **