What a wonderful time of year to go!! Good for you!! Most people will probably suggest going to the Mickey's Very Merry Christmas Party and I can understand why. It has the appeal of being something extra special for the holidays. We were there last year from Dec 9th to 15th and we attended
MVMCP. The fireworks were wonderful and the parade not too bad. Our problem was that it rained, the whole night. It was hard to enjoy everything and we paid all that money, but never got the benefit of the rides etc.. I would probably not go again, but since we have now been it is easier to say. With your children's ages you may want to spend the money on a Character Meal instead.
We did get DDs (3.5) picture taken with Santa in DTD, so that is a good staple. There is a tree lighting ceremony and a reading of the Christmas Story to. I think that is in Epcot. Of course, they have the carolers to. The Osbourne lights in MGM were wonderful and I think the kids would enjoy that, plus the snow!!!
You could each get a special Christmas ornament for your tree at home and have it personalized. If you do that go to the Christmas Shoppe in MK, not DTD. The wait list at DTD is usually several weeks at Christmas time for personalization, but in MK it was just a few hours.
Whatever you do have a wonderful time!!