If you have Admin access to a child's profile, you can manage others' access, this includes removing it. Doing so will not trigger a notification but simply revoke access.
Tap on your profile image or initials (iOS: top left-hand corner, Android: bottom right hand corner) and then My family:
2. Tap on My family:
3. Tap on the child you want to remove a family member's access to and tap Edit:
Note: If they are currently connected as an Admin, you'll need to remove their Admin access first and then remove their access completely.
4. Tap the red circle next to the family member's name and then Delete. To save this change, tap Done in the top right-hand corner:
5. Repeat steps for each child.