Hi Jeffrey,
1/ Although we now know that the Be Our Guest restaraunt will officially open on 6 December 2012, Disney have not yet released the date that it will be possible to start making dining reservations for this dining location.
2/ Many restaurants do normally have special Christmas Menus available although again, this information has not been released at this moment in time. To give you an idea of what might be available, you can check the
Holiday Dining section of the Walt Disney World website to see which restaurants will be offering special Thanksgiving Day menus. I do believe that there is an article called "2012 Christmas Dining Options at Walt Disney World" currently available on the unofficial website wdwinfo.com
but I expect many additions and changes to the list before Christmas.
I would recommend keeping an eye on the
Disney Parks Blog for more information on both of your questions.
Wishing you a magical trip filled with memories which will last a lifetime!