Mac Mini: Using the power button to shut the system down?

I'm not sure if this belongs in hardware or software, but I think this is the best spot for it. If not, my apologies.

I have a Mac Mini that I use as an HTPC, and I'm trying to set it up so that I can loan it to my parents (who are in their 60's and absolutely not tech-savy at all) while I deploy to the desert for a couple of months. I have it completely set to load up Plex and movies from a home NAS when it boots, so that they can watch movies/TV shows to their heart's content while I'm away.

What I'm simply trying to do is make the power button actually shut the system off, so that they don't have to use the keyboard/mouse at all. (Try telling your 65 year old mom to Command-Q sometime ) I can get it to sleep the system, but not shut it down completely.

Is there a setting or so that can make the power button initiate a complete shutdown?

Again my apologies if this seems like a pretty basic question, but my Google-fu is weak.

Cheers!

You're asking for data corruption doing a hard shut down with the power button on a regular basis like that.

I'd recommend setting it up to only go to sleep and not shut down at all.
Then all they need to do is move the mouse or press a button on the Apple remote (if that's what you're using) to wake it up.

You wouldn't catch me leaving my computer with my mom or anyone else that I couldn't teach how to turn it on and off.