What do you think your technically inept family could actually do to your Linux system?

The permission model is such that the most damage they should be able to do, is to an account you've provided to them

Or are we assuming they get sudo and unlimited time, like the typewriter thing?

I'd be more worried handing it over to a experienced person who's familiar with rd.break, assuming the filesystem isn't encrypted

I specifically give family members Linux so I don't have to go clean hundreds of toolbars and the like, as I've had to with their Windows boxen