Restrict AirPlay to single AppleTV out of many AppleTVs on the same network
Yes, on the AppleTV you can set how AirPlay can be used by opening Settings and then AirPlay and then pressing "Allow Access".

On the guest room AppleTV, you would set it to for example "Anyone on the Same Network".

On the other AppleTVs, you would set it to "Only People Sharing this Home" or "Require Password".

This means that the guest cannot send an AirPlay stream to the other AppleTVs, unless ofcourse he gains access to the password, or you share your Home with the guest.