Anything with the date on it will suffice. We brought our wedding program and that was all they needed. Just in case though we also brought our wedding license (not the real one, the "show" one we used during the ceremony). You will also get a complimentary bottle of sparkling wine in your room upon arrival.
Congratulations! You will LOVE Couples! Just want to warn you that there is a very good chance you'll get hooked! We honeymooned at CTI in 2002, have gone back every year since and been to all of the Couples.