Music library sync with child account

I have Apple Music and use family sharing. I also have a young child who uses a device connected under my Apple ID. I want to know how to get separate music on my kids device without syncing my own music to it. I don’t want to delete some stuff from my library but I don’t want it on my kids device, when I try to add stuff to my child’s device it tells me to turn on sync libraries. I only want certain songs and playlists on my kids device but can’t figure out how to keep them separate since their device is set up as a child under my Apple ID.