[hexmiles]

Honestly consider having them offline. I have the same problem and my only solution is me being their proxy for internet. When they need something "online" like movie o buying something, they ask me.

Today most thing happen via a browser instead of programs and it's basically impossible to secure.

Consider using a tablet/smartphone instead of a computer. Apps are a little better than website in term of being "safe". By using something like privacy guard (feature of lineageos) and disabling the browser and email you can keep reasonably safe.

That's what i did. Bought them a tablet, install what they needed (netflix, amazon etc...) and a app for remote control, like teamviewer, disabled browser and playstore, and basicaly everything else. For anything else they call me.

It's not amazing but it work.

Desktop computer are, for me, a lost cause.