I install security camera's for friends and family (as a hobby). There are complete camera systems that can be purchased now for just a few hundred dollars. The system includes the DVR and starts with 4 camera's. I would guess that the total cost would be around $500 including the monitor. If you could request a booth next to a friend(or friends) you could all share the cost. They are extremely easy to setup (even if you just have basic computer skills).
Another option if you are already bringing a laptop is a stand-alone IP camera. These camera's can record to your hard drive or an SD card inserted in the camera. These camera's start at around $75. They also are not very difficult to setup.
I've installed all different types (Panasonic, Vivotek, Samsung, etc.) Basically even the inexpensive camera's would have a great picture for setup you would need.
Here's one that I just installed at our local golf course:
http://www.lorextechnology.com/secur...FQMPbAod13Qz4w
If it were me I would not expect that any security guards would help. The place is just to big. For them to install camera's that would be able to see each table would be incredibly expensive (they will never do it).
If you had your own system you could mount the camera's on a pole pointing exactly where you need them.
I would think the thieves would probably just go to another table if they saw a video surveillance system at your booth.
Good luck!