Hey have you tried Steam Family or whatever it’s called? You can make a new user and they have access to all of your game library. Only one account would be able to play at a time but it would solve your save file dilemma - games files are in the common folder but save files are in the user folder
[EDIT] Steam Families
When you join a Steam Family, you automatically gain access to the shareable games that your family members own and they will also be able to access the shareable titles in your library. […]
Best of all, when you are playing a game from your family library, you will create your own saved games, earn your own Steam achievements, have access to workshop files and more.











That would be even more work IMO
Unless they want to separate their non-game files, too