i had same issues but with a group of kids between 15 and 19.usually they would play in the street and usually would hop the ball of my car that was parked in my driveway.put up with it for weeks,asked them nicely,no good,told their parents useless,even garda and no good,had to get physical in the end and it stopped it,only way to sort it..my friend sorted his issues by pissing in a super soaker water gun and whenever the kids played football and hopped it of his car he would give them a nice blast when they went to get the football.he was well mad as the football had broken his mirror and his sunroof was jammed from the football banging off the roof.