Can you get a video of the children doing these acts? If possible then send a registered cease and desist letter requesting that they stop their children from feeding your dogs (especially food that is toxic to them) as well as tormenting/teasing them by shooting their water guns at them. This might be a way of protecting yourself and provide a legal paper trail. Of course it would be helpful if you could find someone that could put it in what ever language they speak though I wouldn't think that would be your responsibility. I'm not a lawyer so this might not even be possible.
Anybody know if something like this could help in this situation? It wouldn't guarantee it would stop but they couldn't deny you made the request. Now I'm just rambling from being up all night so I'm off to get some sleep.
I would also seriously consider a tall privacy fence.