We've done Christmas at DW for the last 5 years and will never go back to doing it at home. It's wonderful there. The decorations are spectacular and the special events are really great -- even the ones held at the resorts. My suggestions:
Spend the first two days you are there (prior to Christmas Day) getting in whatever rides your group absolutely has to ride because once Christmas Day arrives the crowds come in as well.
Avoid MK on Christmas day (we go to AK in the morning and its rarely crowded, Camp Minnnie-Mickey has all the characters out in their holiday garb and there are entertainers and it really is a great way to spend the morning/early afternoon)
Make reservations for the Candlelight Processional Dinner package either Christmas Eve or Christmas night but do it NOW as space is filling up.
Spend Christmas Eve touring the hotels and visiting with the Characters at each. AKL, WL and GF in the past have had the most entertainment on Christmas Eve.
I don't know the ages of the people in your party but I ship a box of presents directly to the hotel to arrive the day before we get there. These are the presents from Santa. Then on Christmas Eve, after my DD goes to sleep, I go down to the lobby and pick them up to put under the tree (yes I take a 4 ft. tree and decorations with me) for Christmas morning.
My only problem is where to stay this year. My DM will be with us this year and I want it to be very special. I've got tentative reservations at Poly but don't like their decorations and that is important to me. I just can't make up my mind.
Anyway, Christmas at WDW is magical and you will enjoy.