To the OP -- Something you might run into assuming you have 2 separate reservations and you let them know at check-in: In some hotels at least you'll get the bill for your first night under the door the next morning. When that happens I go to the front desk to make sure that their system knows I'm staying in that room. Even when I did that on two different occasions I've come back to my room later that day and found that my key didn't work. The Boston Back Bay actually warned me that this might happen and told me to just come down to the front desk to get the keys issued again.

Not a big deal, just a possibility.