I'm reminded of the South Park episode where they're out hunting... "It's coming right at us! Blam."
I say arm the kids with bear spray and goggles. Wait until the dog gets even with the trailer and yell "It's coming right at us!!" Then spray.
I do understand your frustration though (I was once chased by a dog at night, I got home jumped in my car and went back to even the score but the dog was back home). You're really powerless to do anything. Phone the police or animal control each and everytime it happens. I'd carry a cell phone and call the police immediately after. If you're lucky they'll be able to seize the dog.