Yes, you can add your custom Child Profile fields to the Family Access demographics page. When an Account or Program Administrator is creating a custom field, they have the option to "Include in Family Access". Selecting "Yes" for that item will populate that custom field in your Family Access demographics page.

If you previously set up a custom field but did not add it to your Family Access page, you can edit that previously created custom field and select "Include in Family Access" to add it to your Family Access demographics page.