For context: I personally use a 2015 Intel MacBook running Linux connected to my tv, and use a small wireless keyboard and trackball to control it from the couch. I'm actually planning on checking out KDE Connect after seeing it on https://hexbear.net/post/7662659

I've been researching some simpler options for my own parents since they use Roku which is somewhat limited and has ads. But a mini PC would be too complex for them. They need something with a simple remote and automatic updates. I think an Android box would make sense for their use case. I plan on installing something like SmartTube, PipePipe, or Tubular on it.

If your dad thinks he would like to do something like web browsing, email checking, or gaming on the tv, a mini PC is probably gonna do it better than Android TV.