I haven't gotten any sort of confirmation, but I did just email
DCL and had them link my reservation with the CC #.
I got the following response:
Thank you for choosing another
Disney Cruise Line vacation!
I would be happy to assist you.
Per your request, I have added yours and Erics Castaway Club numbers to your reservation.
I am unsure if your upcoming cruise, which is the Boys & Girls Club Benefit Cruise on January 21, 2011, will count towards your membership.
Therefore, please contact the WDW Special Events Team at 888-885-3700 for additional assistance regarding your special cruise on the Disney Dream in January.
I hope this information has been helpful.
Have a Magical Day!