A house over the back of ours have been having a BBQ since mid afternoon. They've been playing music and the children have been out playing for most of the day. I'm estimating the children are over 5 years old having seen them biking up and down the road this afternoon. I have a 1 year old who sleeps in the back bedroom and despite the window being closed (which I would rather it wasn't because it's 27°C in their room), the sound of the group of children constantly shrieking and screaming has woken my toddler up twice already.
I'm not for one minute suggesting kids in their own back garden should generally not be allowed to make noise for the sake of neighbours, at the end of the day I have a 1 year old who will squeal running around the garden in the afternoon. But AIBU for thinking that past a certain time (10pm) the parents, who are out there with them, should at least be asking them to play something that isn't riling them up so much?