Yes, you can send packages ahead, and when you check in there will be a note on your reservation that you have a package waiting for you. The check-in desk will either retrieve it for you, or you have have bell services deliver it to your room.
Have it sent to the following address (replace the stuff in blue with your actual info):
Your Name (Guest)
Disney's Caribbean Beach Resort
900 CAYMAN WAY
HOLD FOR GUEST ARRIVAL 11/09/08
LAKE BUENA VISTA, FL 32830-8411
I would send it so that it arrives within four days of you checking in, as the resort won't have your reservation in their system before that.