Good luck! I had to deal with the same kind of situation when we moved here. Between the neighbors on either side of us and the one across the street there were 10 kids who played in our front yard - thank goodness the back was fenced. That didn't always stop them though, they would climb our fence to get their balls or to "look around" and that was big no-no because we have an inground pool. It also didn't help that the school bus stop was suppose to be across the street at the stop sign but the kids all stood in my driveway so the bus picked them up there so everyone just assumed my yard was the stop. (I fought the school, bus driver and parents over that for years - if it rained they stood on my front porch at 7 am!!!!). Anyway, after they destroyed my landscaping and knocked a hole in my garage door playing hockey in my driveway I finally had a enough and had to chew them out. I had asked nicely for months for them to stop playing in my yard but when the parents didn't care and I was the only one with a concrete drive which made their puck slide better I got nowhere. We even had to take our basketball goal down to get them to stop coming over.

Anyway, I got the knickname of wicked witch of the neighborhood but I don't really care. It never really stopped until all the neighbors with the kids finally moved away over about a 6 year period.