Just thought I would offer the idea that "parental controls" allows you to configure how a particular account can be used, allowing (or blocking) access to apps, and files on your Mac.
It's not really about children, but for any user of that account. You can control how the account is used - so you could think of "Parental Controls" as "Account Rules" for any standard (including Guest) account that YOU can enforce.
As you admitted to wanting to limit "certain files" from public view, Parental Controls will provide a "managed" solution for that. I have settings that prevent access to my banking files. Not because I don't want anyone to see them, but simply that I don't want anyone, other than me, to make changes. Parental Controls provides that feature.