I love the fact that you are such a great neighbor. Mine is a monster. It seems like everytime he came over he was complaining about something. Obviously we avoided him. He was sort of respectfull to my husband, but was very aggresive with me when I was alone. The city ended up citing him for frivolous complaints against us. He really started to scare me. After a few conservation from 3rd parties who intervened, they determined he felt slighted by us. Wierd!
I’d say your neighbors are lucky to have you, and you may want to somply hint that your tenant may complain about the balls so tell him to please be carefull. Good luck!!!