The Christmas activities continue past the last Christmas party. I’m not sure which activitice are special to just the party, it’s been a few years since we were there for Christmas. I know we saw the Christmas parade on Christmas eve.
How much after Christmas are you looking at? Between Christmas and New Years is super busy, in fact, it’s crazy busy until the kids are back in school. I remember looking at wait times last year around Jan 3-6 and it was insane. Crowds die down fast after schools start up again (1/4/16 for most schools around me) but then the Christmas stuff is done and starting to come down. When we were there for Christmas we could easily see the crowds building each day through Christmas day and I hear the week between the Christmas and the first of the year is the highest crowds of the year. When we went December 17-25 was far busier than we’ve ever seen in May, June, or July.