FYI, I had to cancel one of my preorders because it was not tied to my origin account (they ended up making a new account for me and I didnt want two origin accounts to juggle). If you cancel you will have to wait more than 48 hours before you can redeem a new game code. Seeing that they are busy with the launch atm, I'd bet good money you'll have to wait a while before the system allows you to re-register with a new code.
Moral of the story- cancel now so i can get in earlier.