Hide behind one of the cars with a large kitchen knife, when the ball comes near enough for you to grab it get it and just go psycho on the thing while shouting out all kinds of insults. When it looks like crap throw it away from the kids and just stare at them, knife In hand, with a crazy smile on your face. Have a camera phone ready to take a picture of there faces and upload it here so we can all laugh. If they know what's good for them they'll never return, and everytime you happen to walk past one of them they'll be ******** themselves!
Works every time.