You can update personal details of members in your household aged 18 or under in your household account settings.
Go to your ‘My household’ section and select the three dots next to the person’s name you want to update and select ‘Edit details’:

For members aged 12 and under you can edit their name and venues.
For members aged 13-17 you can edit their name, venues and email address.
Please note that you cannot edit the details of any 18+ members in your household. Those members can edit their own details in their advantage account using their own log in details.