Some of the members accept private messages. I do not.
From what you have posted here, I can tell you that the neighbors probably think you are a snoop, but nothing you have described here is an invasion of their privacy. If you were to peer in their windows or take photos of them inside their house or record their conversations without their knowledge or use binoculars to keep them under close watch, then those would be considered invasive. But looking out into their yard through the window of your house, even if it is to keep an eye on these wild children and their plain-view activities, is not an invasion of privacy.
I suggest that if you see the neighbor children doing something dangerous, you contact their parents (if you have a civil relationship with them) and/or the police.