Procreate (one time purchase) + pictures of real coloring books might work. You can also get PDF coloring books and load them as layers. As far as I know Procre

Procreate (one time purchase) + pictures of real coloring books might work. You can also get PDF coloring books and load them as layers. As far as I know Procreate has nothing in it that should cause problems. It can access the file browser, but that might be controllable in parental control settings.