You know, I just had an inspiration on this thread.
Is the do-nothing sheriff an elected official? Most places he is.
Before spending thousands on a security system that will only produce evidence the sheriff won't act on, and figuring ways to go over his head, take the easy way.
Have your wife arrange to meet him socially, and tell him she wants to make a contribution to his re-election campaign. Do it, then wait a month or two, call him up and tell him those dratted neighbors have done something again. For about 10% of what the security system would cost he will come out and take care of the problem. I bet there will not be another instance of vandalism.
No this isn't the way things are supposed to work, but in most areas there is a very strong "good old boys" network. The neighbors are part of it, and this is the quickest way for you to get into it.