Jim,
I got a Chromecast last week, so have only played with it a little.
Your Chromecast device will have a number when you set it up. When you ask the computer to cast to a TV, you pick the correct device. So, I think if you had multiple Chromecasts, it would not be a problem. It would be a bit of a pain to move the Chromecast, it needs to be placed into the HDMI port and connected to a power source, either USB or a regular outlet. The Chromecast uses your wireless network to receive the input from your computer.
