Hi Julie,
I'm super excited about the online check in feature for Walt Disney World Resorts, I can't wait to try it myself.
From what I've learned, you simply enter your reservation number and telephone number at
www.mydisneyvacation.com and you will be prompted through the check in process. You will be asked online to confirm all of the information applicable to the reservation (names, addresses, credit card # etc.) and will have to review and accept the terms and conditions.
Upon arrival at your resort, there will be a separate line at the check-in counter for those that have completed the online process. You'll simply show your photo identification and will then receive your room keys and Walt Disney World Resort information package. Simple!
I'm anxious to hear some first hand accounts of how it's going. Good luck and have a great trip!