Yikes! Sorry about your bad luck...are they just punk kids or something?

Ever thought about getting a guard dog? Seriously, that would be a great preventative. The first time they got their leg chewed off by kujo, they won't be back

What about putting a fence up? Motion sensitive security lights? Definitely put a sign up saying property under video surveillance and maybe "no trespassing, violators will be shot" for good measure.