Divide into two teams and have both teams sitting down in a row (either on floor or on chairs) facing each other. If the group has arrived and is sitting in rows facing you can divide the group up and get both groups to turn their chairs to face each other. Using a balloon as a ball, teams remaining seated have keep the balloon in the air (unlimited hits each side). Points are scored when a team gets the balloon over all of the opposing team and hits the wall (indoors) or beyond a boundary (outdoors). Points also gained for when balloon lands on ground.
See also Number Hockey for a different more energetic version.