I wouldn't waste my tome with IR camera's. The purpose of those is to catch someone in the act but isn't the real purpose to prevent the act in the first place? If you want to go the camera route then I would put them where they are easy to see, cover what you want to protect, and hard to get to. Then I would use regular floods with motion sensors to light the place up if someone comes onto your property. Nothing like bright lights and camera's to make some rethink their actions.
I use my X-10 system for this. It keeps the floods off when the Holiday lights are on and activates them when the Holiday lights are shut down for the night. Since many of my floods are X-10 lights, they send a signal when they turn on and I have the system turn on an inside light during these times that is visible from the street a few seconds later so it looks like I am coming to see what is going on even if I am sound asleep. Thinking that someone is coming out is even more of a deterrent.