give them a desktop that is basically xubuntu amd64 (xfce4 desktop on xorg) + firefox + chrome, and then install all of the best adblock extensions in both browsers. Even the most clueless parents can't successfully download and run windows binary malware/ransomeware/viruses on that. the xfce4 GUI is close enough to traditional windows98/windows2000/winXP models that most older non technical users have no problem wit…
Also might be useful to get a hosts file mapping bad domains to localhost