To make the game even more like real polo, have the kids ride broomsticks like stick horses while they play the game. It's always advisable to have a few extra Ping-Pong balls on hand. Determine a beginning point in the circle and place two bags there. In one bag dump a number of marshmallows. The other remains empty.
Kids toss the marshmallows around the circle.
The person at the end of the circle next to the empty bag then drops the marshmallows into the bag. The team has one minute to see how many marshmallows they can get around the circle and into the bag. For an interesting twist to this game, have a member of the opposite team seated by the empty bag, and as the marshmallows are fed into the bag, he eats them as fast as he can. He can only pull them out at a time with one hand. A fast eater can get the final count in the bag to a minimum.