How should I handle my new, annoying neighbors?

The 3 kids are unsupervised, outside screaming and playing in the road until 10 or 11pm every night. They have hit cars with and skateboards, they jump fences and run around in other people's backyards, they dump their garbage in other people's cans (beer bottles and Ramen noodles, real cl) and they have people with more kids over all the time. Mom's boyfriend shows up every evening with a 40oz and drives home later, and, there's a blue car that comes by 3 or 4 times each evening with a young dude in it who never gets out. We think the Mom may be buying drugs, but of course we can't prove it. We have asked the kids to stay out of our lawn with their baseball bats, and so far they have, but they are terrorizing the old lady who lives next door to them (they're across the street from us). Should I try talking to the Mom? Call the cops? WHAT? I don't think the cops can do anything unless they see the kids in action. I don't want to cause problems but they are out of control!