It’s a real football, not a nerf.
Yeah Nerf pretty much only makes toy guns now. But the basic idea holds. If they didn’t break anything what’s the bother? Kids will be kids, and kids will miss. And if you get the reputation for being the grumpy neighbor the kids will torment you. Our area’s grumpy neighbor would freak out if anybody got close to being on his property line, if one of our toys got even a foot on his property, even so close we could get it while still being on the sidewalk, he’d come out yelling at us. Everything that hit his property was “gone”. So one day one of us grabbed a notepad and we started making paper airplanes. Technically we weren’t throwing them onto his property, but we sure didn’t mind if they landed there. And of course we didn’t retrieve them. So then he throws one of his fits and starts yelling until parents come out, complaining about all the paper airplanes all over his yard. And our answer was “well we’d clean them up but we get yelled at for even being on your sidewalk”. Somehow he managed to not have a heart attack over that one, and he actually toned it down a bit, and we could actually retrieve some of our toys. Never stopped being the grumpy neighbor though, and we never stopped hating him.
The moral of the story being, if they didn’t break anything don’t turn it into a confrontation. You’re out numbered, the neighborhood kids will win. Ask them to be a little more careful, keep it calm, and the neighborhood will remain peaceful. Keep turning it into yelling matches and someday you’ll find dozens of airplanes decorating your yard.