look man in all honesty you have to come to terms with some things.
1. you need proof for cops to get interested. this means setting up security cameras to catch the action you accuse others of.
2. your kid for now at least, can't be in that room if you feel the way you feel and if you are very sure you are going to fire rounds off in that direction. either move the kid, or don't shoot in that direction- which you can't possible guarantee will happen anyway.
3. i go to the dollar store, and get these magnetic alarms. they cost a buck each.
http://cgi.ebay.com/Wireless-Window-...item3a55a2f2d5
look just like this. put some on your front door. back door, windows, whatever. the battery won't run out even after a few months, trust me i know.
4. go have a talk with the owners of the place. share your concerns and such.
5. have your dog trained. the dog is the best alarm. they know when people are coming sometimes 50 if not 100 feet away