I concur with ellylex.
What I would do is make two reservations. I would make the reservation for the second night first and record the confirmation number. Then I would make the reservation for the first night and put a comment in about the reservation for the 2nd night along with the e-mail.

Make sure you book the same room type each night. It is highly unlikely that you will have to move. You may have to sign a new guest card for the 2nd night, which a quick stop by the front desk on the second day will solve. Just ask about proper procedure on checkin the first night.