We did something similar but I got too lazy to synch up.
We re-purposed a Mac-Mini that we were no longer using. It is mounted on the wall (they sell these on Amazon) and is directly hooked into the TV via an HDMI cable. We can control with the Apple keyboard and mouse. Alternatively, because we also set up an internal wifi network with an old router, we can control with an app on our iphones or ipads.
Movies are ripped onto the Mac at home and added to the media library. I usually then just copy it onto a flash drive and bring it with me to the trailer each time to add to the trailer's Mac Mini.
In the bedroom, the content can be streamed via wifi from the MacMini to an iPad connected to the bedroom TV using Plex as a server.
Originally thought of taking one of our 3 AppleTV's from home, but figured that it wasn't worth doing if all I needed was to stream content from the MacMini. The iPad is where I usually download content and with the Lightning to HDMI adapter, the iPad plugs directly into either TV. There's also a wall mount for the iPad in the bedroom above the TV.