I feel your pain, and was in the same EXACT predicament. Here is what I came up with after lots of trial and error...
First, moving them from TV to TV was not only a PITA but it was taking forever to get the streaming sync'ed back up and lots and lots of restarts after every move.
I purchased 3 ATV's, one for each system. Hooked them all into the same iTunes account that is constantly running and open on my iMac. I have no problems or issues watching content on any given TV and one little thing I discovered, that was NOT advertised, but makes total sense -- pause a movie I am watching with my ATV in the Family Room and go to bed, turn on ATV there and it Resumes where you left off. Again, simple enough to explain but dagnabit if I wasn't excited.
Here is where I encountered issues...iTunes only lets you authorize 5 devices to your account. So do the math, 3 ATV's, 1 iMac and my MacBook Air and aww snap, I am out of devices. Well I also have an iPad2 and my iPhone. For some reason my iPhone doesn't count as a device, and I haven't figured out why, but the iPad does. So what was happening was iTunes was using like a rolling authorize. It was strange and would love an explanation, but anyway, it was then locking up any given ATV as an authorized device. ARGH (ended up deauthorizing the iPad)
But now everything works great, except for that pesky reset after sleep issue, but that's not related to your question and I posted it elsewhere already. Don't know if that helps or hurts