Just thought I would post the response I got from Member Services today when I asked about the Merry Mixer on Christmas Day (I really want one because it fits in my plans so well and it's our only Thursday during our trip).
Dear XXXXX,
Thank you for contacting Member Services. We have not been given any
information on whether or not a Merry Member Mixer will take place on
Christmas Day. Please check the Members Only website from time to time
for more details as we get closer to your stay.
Sincerely,
Todd
Member Services | Online Communications
Disney Vacation Club