J.J.
I am sorry you are dealing with this. I had this happen last year a 9yo and 4 yo who lived next door. I have a fenced in yard, but they would come in. It started with the 4 yo who would just show up alone in my yard. He was almost never supervised in his own yard and apparently got bored playing by himself and would sneak over even when we were not outside playing. Then his 9 yo sister started coming over. I would tell her it was time to go at times. I never spoke to the mother about it. It did bother me a bit, but I tried not to worry about it, they are not my kids and I just told them at times they had to go home. They finally moved away, so I didn't have to continue to deal with it. I would tell the kids it is time to go play in their yard, say you are having family time sometimes. Once in a while is fine, but not constantly. Things were different when we were kids, we went all over the neighborhood to play and visited many houses. Now kids can't do that anymore. It is a completely different world. When we were kids we respected adults and if we asked about playing there and were told we respected that. And people felt fine saying both yes and no. Anyway, sorry you are dealing with this, but i would try to start setting some boundaries at least with the kids.