Hi Kj1719,
Thanks for posting in Apple Support Communities.
When changing the birth date for a child, the family organizer will receive an email to approve. If you have scrolled completely down in the email and don't see where to approve, try opening the email from a browser or different mail application, just in case there are restrictions to prevent all content of the email from showing.
If you're still not seeing the area to approve the request, try repeating the steps to send the approval email again.
Change a birth date for a child
To change a birth date to any age below 13,* you must be a member of a Family Sharing group, and your family organizer must approve the change. After you change a birth date to any age below 13, you can't edit it.* Learn more about Family Sharing.
1. Update the birth date.
2. Follow the onscreen steps to send an email request to your family organizer.
3. Your family organizer will get an email with instructions to approve the request.
*Age varies by country or region. If you need to change the birth date for a child, contact Apple Support.
Update the birth date associated with your Apple ID - Apple Support
Regards.