No, you don't need the card, code or anything to book the room, only when you check in (in fact, many people have reported they were never even asked for the card when they checked in, but I certainly wouldn't count on that). If you already have your dates, I would call right away, as they only set aside a certain number of rooms at that rate and the longer you wait the less your chance of getting it. Alternately, if you are somewhat flexible with your dates you can ask if they have the rate for the week before or after. Good luck!