to commonly asked questions.

Can't make changes to my child's parental controls to log out.

I went thru the steps we discussed and, though I can now view the Apple ID settings, the sign out portion is still greyed out “due to restrictions.” Do I need to turn off Screen Time for that family member completely?

From Wife’s phone you should be able to go to Settings/Her account name/Family Sharing/Screen Time/Child’s name/ the select to turn off screen time. Then on child’s phone perhaps turn off then back on again and you Should be able to make changes. Let me know if not. You could also send me a screenshot of the setting that’s still greyed out. Or just take a pic with your own phone.
This image is a theme.plist hack