Help with offgrid (power, no internet) "streaming"

I'm looking to create an easy solution that is child/wife friendly. I'm hoping to get a set up going without internet. I however would like it to run like a Chromecast with plex.

I was thinking of a

Dell Optiplex 3020M Mini PC USFF, running windows 10

An external hard drive with content.

From here is where I have gaps. Could I set up a plex server offline on the device, with plex media player and use an Flirc remote with pre-programmed buttons?

Essentially, I'm trying to create the experience of watching Netflix on a Chromecast but with plex and a pc remote control of some sort (with pre-programmed buttons that load up content so kid and wife only have to press one or two buttons to get to their shows)

Thanks!