The Retina IIc's Synchro-Compur shutter has M/X flash synchronization. There is a standard sync post on the side of the shutter assembly. I don't have my Retinas in front of me, but I think there is a small light-green metal switch that you would use to switch between bulb and electronic flash.

I'm not entirely sure about setting up a light system on a stand, but as long as you can plug one of the units into the sync post and slave the other, it should work.

The f/2.8 Xenon is a nice lens and should give you some nice portraits. I'll be interested in seeing the results.