How many jacks do the TV's have? The easiest solution would be to use a y-splitter to connect all systems to both TV's at the same time. So each cable coming out of each system goes into a y-splitter, and each arm of the y-splitter goes to a different tv. Then you just use the TV's internal input selector to pick the system. If you don't have enough jacks on the tvs, you would need to get a manual input switcher, which is about $20 at radio shack. In short, both TVs are getting the signal from all 3 systems, you just set the TVs themselves to display the signal from different systems depending on what you want.
Analog y-splitters are cheap, $4-5 for the overpriced ones they seem to be selling nowadays. I am not sure about HDMI ones though, but you can get HDMI stuff cheap online (the stuff in stores is once again really overpriced, but you have a better shot at radioshack).