There's a little kids playground near my home - it's walled in, full of slides, bouncers, climbing frame and other little kid stuff. Mostly preschoolers or younger kids from the nearby primary school.
The other day three older children (I'd guess 10/12) were playing football in there by kicking the ball incredibly hard against the brick wall so it ricocheted everywhere. A few times there were near misses where the ball flew up into the air and nearly hit various adults in the head. There was a degree of mutual eye-rolling but no-one said anything.
I was pushing my daughter in the toddler swing and they began playing very close to us. The ball whizzed past her head a couple of times and I asked them very politely to be careful. Then it got me in the back of the leg very hard. I shouted "ouch!" And then turned round and told them firmly not to do it again. I carried on pushing my daughter and once again got smacked in the back of the leg; this time I was a bit less calm and told them to stop it now. Almost immediately it hit my leg again, this time I felt sure it was deliberate so reminded them there is a big public park with football pitches 5 minutes down the road, and that this playground is for little kids. At this point the mum with them finally took an interest and told them to be careful, saying very pointedly that this playground "is for everybody". Little tyke was giving her a lot of backchat incidentally, I was quite shocked at how rude he was being to her. It felt a bit awkward so me and DD left (no doubt to everyone's relief!)
So I know I was "the bad guy" for not just doing tinkly laugh, kids will be kids - but WIBU?? Why play football ball in a tiny enclosed kids' playground with toddlers running all over? And why let your kids whack someone else with a ball three times before bestirring yourself to do something about it?