John is correct in regards to your options. Given that it is a small system, I would opt for the LV motion sensor from RAB over the ABT system. It is far more simple and cost effective.
The ABT system, while effective, can be a real challenge to install and set up. It also doesn't blend in or 'hide' very well.
All that being said, I am not a big fan of motion controlled lighting. If the system is designed well, it should provide for safe, secure, effective and efficient lighting that is unobtrusive. If all night security is a concern, have the system come on a dusk and off at dawn using a astro timer. The client will not have to be concerned with potentially finicky motion detectors (aimed at the wrong spot?) and if you are using LEDs, the electrical draw will be minimal.
Have a great day.