Yeah, the fact that these kids are going in and out of whatever yard they want puts a completely different face on things.
My back yard, where I allow my dogs out, is completely fenced. Both to keep my dogs in and other people out...no one but Anthony and I (and guests we invite) has any right or reason to be on our property. My front yard, however, is open, and unfortunately that seems to make people think I WANT them to come into my front yard. People have let their dogs mess on my lawn and not cleaned it up. Last summer I recall even posting here about a kid living up the street who used my lawn to turn her bike around. People have come right up my front lawn to my side gate to see my dogs. I'm thinking that as much as I don't want the expense and trouble of it, I may have to have a fence put around my front yard as well, because no matter what I say to people (Please don't let your dog mess on my lawn, or at least clean up after it, please don't roll your bike up onto my lawn, it's leaving tracks on the grass, etc) people still seem to think that because there is no physical barrier there, it's their god-given right to come on to my property. My neighbours (the ones who tore down the fence without telling me, some of you might remember that saga) have even gone so far as to tell me I have to get rid of my dogs because they don't like dogs. They've even threatened to call Bylaw/animal control on me. I tell them to go ahead; I'm not breaking any laws. All my pets (including both indoor cats) are licensed and registered with the city and I'm within acceptable numbers (numbers within city limits are limited to 3 dogs and 6 cats. I have 3 dogs and 2 cats). I think I frustrate them because I won't be intimidated.
It sounds like the issue here has gone far beyond invisible fences or the presence of dogs. I hate to say it, but brace yourself, Snowdragon. If the parents of these kids are so entitled that they think their children should be able to play in any and every yard in the neighbourhood, trouble with this family may be just beginning.