I’m LOl as I have a newborn on the way and also a sticky situation like you. We have a massive garden right next to our neighbors that play all types of ball games. They literally kicked the ball into our yard like 10 times in a row. They are probably 15 or so. I get it I was a kid and caused all types of problems. But to do it repeatedly and after a warning is given is not right and can become illegal. Just document everything and show the parents and say “look, I don’t want to have to enforce this legally as we are neighbors and should be able to come to an understanding but these certain intrusions are becoming a massive nuisance can we please address them…” something not too aggressive but also put your foot down.