I think this is fairly well solved from a mathematics point of view (high-school level k-means clustering). The unsolved bit is simply how we get the Spotify et al. product managers to care.
All they need to do is filter out content with genre=kids from recs. They could create a separate kids recommendation item if people actually want that.
This wont happen whilst they have family and kids’ account types. Charge parents more for the premium option of not filling their carefully curated genre recommendations with nursery rhymes and Ed Sheeran.