I am not sure about individual restaurants in Canmore, but some choices would be places like the Radisson Hotel and Silver Tip Resort restaurants.
I am not sure if you are willing to travel to Banff, but it would offer more options. I believe the Maple Leaf Grill and Banff Brewing Company are both offering Christmas dinners. There are also more places like the Banff Springs Hotel and the Rimrock.
Try contacting the Canmore Visitor center to see if they know of any other options. Their phone number is 403-678-1295 and the website is here: http://www.tourismcanmore.com/
Hope that helps you some, have a lovely Christmas where ever you end up:)
Edited: 12 December 2011, 6:13