You don't need to be there for Christmas. Starts the Fri. after Thanksgiving and goes (I think) through New Year's. It was one of the most extraordinary concerts I have ever been to. We have been three times and each time I still get goosebumps when certain songs are sung and tears when Silent Night is sung in German (my greatgrandmother and grandmother would sing it to us in German). The orchestra is phenominal and to hear the 400 voice choir sing is a "once-in-a-lifetime" event. It is even better when you get an enthused guest narrator tell the story of Christ.
If you are there anytime in that time frame, consider seeing it. I would suggest doing a Candlelight Processional dinner package. That way you are guaranteed a certain section of seating instead of waiting in line sometimes for over two hours to get a seat (and even then if the theatre fills-up, you may have to wait for the next performance).