Awesome work, I love seeing how much is being done in terms of onboarding processing with ARM computers.
One of the approaches 3574 took for 2013 after getting blinded at one of the events in 2012 was switching over to IR for the retro-illumination. Our camera of choice is the PS3 eye, and there are many tutorials online for performing this conversion. The other benefit of this is that the value channel can be used directly. Simply taking the red channel is a close enough approximation and very fast.
For power of our Odroid U2 last year, we used this from Pololu:
http://www.pololu.com/product/2110
even as low as 8 volts from the battery are enough to work with a buck power supply and they're considerably cheaper. 3.5A was also enough to drive a separate powered USB hub, as we ran into stability issues with 2 cameras.
As far as hard poweroff, that's the way we went as well, however this article from Bunny talks about potential issues with hard power removal:
http://www.bunniestudios.com/blog/?p=2297