Hi Mike,
As stated above, security is the first thing to sort out before cameras and you seem to have this sorted. Cameras are only any use after the event and good security should stop the event happening in the first place.
For what it's worth, we had problems with kids at work entering the yard by climbing over the gate and getting up to all sorts of mischief.
The local Crime Prevention Officer advised using something called 'Vandalene' which is an anti-vandal paint. It's black and you paint it on in places where the people enter and because it never dries, they will get covered in the stuff. Apparently, it's impossible to wash off completely so the police can see it on their clothing after the event.
Since applying it about nine months ago, we've not had any more incidents.
Hope this is of some use,
regards
brian