How can I change the age on my child’s account?
How can I change the age on my child’s account?
Apple support's article (link below): How to:
Update the birth date associated with your Apple ID - Apple Support
says:
"If you need to change the birth date for someone below age 13, contact Apple Support.*
*Age varies by country or region. If you need to change the birth date for a child, contact Apple Support.