England Supporters Club

Both my son and I have been successful in the ballot for the Czech game ( after being unsuccessful in every other ballot) . I know it's still a long shot  2800 chasing 753 tickets BUT if I want tickets together do i have to add my access code and then add ticket to the cart and then go back in and add my sons access code to get the additional ticket ( that is if there are any left by the time i do that) or is it best to both do it separately and he log in using his access code and me mine. The problem is if he gets a ticket through this method and i don't , he won't be able to go as he will have no transport ( we live up in the midlands) to get back. Can he 'sell the ticket back if that happens. Ditto if I get a ticket and he doesn't , i won't go as the Father and son bond is to go together or not at all. Any ideas/a advice would help.