Custom domain was added before starting family account

As the subject says, my custom domain was added and configured before I started using the family account. I would now like for my wife to be able to create aliases for the custom domain too.

Do I just need to delete the security key DNS record at my domain provider and then go through the process of regenerating the key (this time selecting the option for "All family members can create aliases for their own domain." or is there something else I need to change?