I think what's confusing everyone here is that we don't understand what you mean when you say you have "one computer doing all of your a/v." How is the video getting to all of these TVs? You say they're not clients; are they smart TVs that you're streaming to?
Or are they all directly plugged into the one computer via HDMI or something (i.e. you effectively have a multi-monitor setup with several TVs in different rooms)? If that's your situation that's a pretty unusual setup, and that may be why some of the advice may not be hitting home. It would help if you could clarify.
If you are effectively doing a multi-room multi-head computer, running multiple instances of the same version of MC (i.e. running MC20 two or three times at once) is probably close to a good solution, but you may run into trouble with that. If it were me, I'd set up several virtual machines and run a separate MC in each one, which is probably the "right" way to do what you're doing.