You have options. It may be worth trying them all.

1. call the cops after having asked him to desist. You MAY be able to
get a restraining order based on reckless endangerment to the kids.

2. Put up a net on the fenceline. Probably 10 foot + poles and net.

3. Find out who he has homeowners insurance with. Then speak to his
insurance company claims department and advise them you intend to claim
on any and all damages resulting from his conduct.

Do not retaliate in kind. You need to keep the high ground if it goes
to court.