Make a line of cones down the center of the field.  Split the kids on either side of the line.  Every kid gets a ball, and have extra balls if you can.

Kids try to kick as many balls as they can across the line.  If someone kicks the ball to their side, they run and get it and kick it back.

After a couple of minutes, stop the game and see which side has the fewest balls.  They win the round.

This is best played on grass, which will stop the ball rolling.   If the field is not flat, split the field so one side does not have an advantage.