In your comment, is allowlist a list of videos only they can watch? (not a list of 'age ranges' or 'channels', but actually being able to select individual videos). I was never able to get something like this out of youtube kids when I've tried it in the past.

All these services curate for kids and I want to choose what my kids watch, so they are all failing me. (I'm with the others who go with YT premium, youtube-dl, kids watch with vlc or something on a tablet).