Was at DL 17, 18, 19 Dec last year.
Didn't find it too bad at all. The only parade we watched was the Xmas one in the afternoon, just stood on Main Street about an hour before start and had front row spot. Kids sat on kerb and we took it in turns going off for little walks. But be warned people will invade your space, so might be best with little kids to sit them on kerb and you stand behind them.
My kids were 17 and 15 and have been to DL lots of times, so they were not really interested in the parades and shows, we used that time to go on rides.
It did get crowded, so you should have a bit of a plan.
We had 3 day hoppers, stayed across the road from Entrance.
Maybe just look up what rides and shows you want to see and then do it by land.
Write down which ones you can get FP for, so u know.
Make sure you go onIt's a small World, decorated beautiful for Xmas and for Carsland you have to go to Calif Adventure on opening and grab fast passes, they go quick.
We managed to ride that 4 times in our 3 days and did Toy Story 3 times, another one that gets big crowds.
Having older kids we did do single rider on the rides that have that, makes a difference.
Just to let u know the weather last year at the time was cool, especially mornings and nights. We also had a bit of rain.
We then headed to WDW on the 20th and after reading up on that and how crowded it got, I was dreading the thought, but that also was fine, we had a blast and did everything we wanted.
Have a great time and go with the flow and I am sure you will want to go back for longer another time.