Hi gtarplyer,
I can answer a few questions for you
The Sony cameras are great and very fast, but I would not advise you use them for this application, the problem is Sony's proprietary connectors for triggering and Breeze or Smartshooter currently do not support downloading of images from Sony cameras (Sony are very guarded with all their SDK info that would be required to make this happen)
I would recommend Canon DSLRs for ease of finding trigger cables/adaptors (simple 2.5mm stereo jack) and cheap PSUs...... the best at the moment in terms of cost versus quality is probably the 100D.
Triggering via USB is not a good idea as, yes as you mention it is not possible to trigger all shutters at exactly the same time.
The ShutterCell I can of course give you plenty of info about
There is a ShutterCell info sheet here:
http://www.esperdesign.co.uk/assets/manual-_sc.pdf If you used one of our ShutterCells you would need something to trigger/switch the input, most people use one simple radio remote for this such as the Pocket Wizard, this means you can be anywhere in the room (or in the middle of cameras for a 3D selfie) and trigger all the outputs without getting tangled up with the cable.
You could of course just use a simple cabled remote into the input if desired, but beware any that have half press AF function, as even if you have AF turned off on the cameras(as you should) the signal can disrupt some cameras and lead to unreliable shutter control.
For large camera rigs it would be cheaper to use the ShutterCell rather than one PocketWizard for every camera, plus you don't have to worry about batteries on the PocketWizards.
You will still need Smartshooter(cheaper) or Breeze to download the images to your attached computer unless you don't mind taking memory cards out to copy the images over, though this is time consuming and risks moving your cameras.
Hope that helps,
mala