We have been twice in the last 2 years just days before. Last year was the 18th to 23rd. Year before that was 17th to 28th. I have seen the crowds before and after Christmas. Of course much better before. The days before no way compare to summer crowds. I have been all of my other 8 times in the summer. Summer crowds are bad. The week before Christmas is much better. Now I am not saying walk on rides, but not summer by any means. We saw wait times at TOT, MS, TT, and other very popular rides hover over an hour. Fast Passes were gone by late afternoon for most of these rides. You will need to use FP for the more popular rides. We thought EE was a waste. So many people from the resorts. We didn't manage to get any more done on EE days with the exception of one EE at EPCOT. MK forget it. Later in the evening we managed to ride Buzz 3 times in a row with just walking on, but this was near closing. We didn't notice a real increase in crowds until after the 25th the year before. Crowd levels were about the same before that-manageable. So your days should be good. The most unpredictable thing is the weather. We had days of shorts and days of long pants and winter coats this last trip. Year before we had short/capri days with only jackets at night. You never know. I always pack more for my December trips.