I was thinking of doing something like this. My first idea was the parent manages a sort of simulator (farming, civ, city, idk) and the child is a little chaos agent that wrecks havoc.
But you might get the reverse, parent frustrated kid bored
It is a good idea. I can't have my kid play poe and I am checking out too quickly when I let her play pattern matching games. I personally think this is a niche in Steam that has not been 'occupied' well yet.