I've never checked in that late, (checked in around 11PM, but didn't call, because I knew it would be before midngiht) but I would probably call the resort to let them know it will be an after midnight arrival. Your reservation is usually enough, actually, all they've ever wanted from me was my drivers license, they didn't want to know my reservation number at all. That goes for value resorts as well as DVC, I've never needed to show my reservaton.