I've accidentally made an on-business booking for a child that is actually over 16. I worry that this would create problems at check-in as, as I understand it, there is a difference in taxes of about £5. I called on-business - was told they could not and they added the DOB of the child pax and said it is no issue at all. The online system accepted the DOB without an issue. I still worry about something going wrong at checkin etc. Any thoughts?