I am not the expert, but these are just my thoughts:
The week between Christmas and New Years is notoriously the most crowded, so I'd imagine the 26th and 27th will be packed. I think Christmas day would be packed as well, but my gut feeling tells me that a lot of people would be spending Christmas day with family. In the evening it might get more crowded, but maybe the day wouldn't be too bad? Again, this is all just conjecture. I've never been during that infamous "crazy week"