We will be there 3-7 and I have been in the begining of December before. Thursday during the day should not be to bad. Friday day may be a bit more busy. At night though many, many locals and anual pass holders come in after work for the Believe Fireworks and snow. It gets very crowded. Fantasmic will also be presented on Friday and Saturday night which will add to the crowd. Saturday during the day at
Disneyland will be crammed and almost unbarable in the evening IF you are not prepared ahead of time for those kind of crowds. We will be doing Disneyland on Thursday and Friday and then going to DCA on Saturday which won't be nearly (hopefully) as crowded. Make sure you get to Disneyland before opening time and get in and ride as much as you can in the morning and early afternoon. You can do much better when you are solo. The Christmas decorations will be up and the Christmas Parade will be presented. The Holiday version of the believe fireworks will go everynight and there is snow as part of the show. The snow works best and is much more plentiful, on Main St. The Electric Parade will be on Friday and Saturday night at DCA.
Good places to eat at Disneyland.... The Blue Bayou (reservations recommended), The Plaza Inn, Redd Rockets for pasta and salads (not the pizza), The French Market.
At DCA good places are Ariel's Grotto ( character meals) The Trattoria at the vinyard was fine but not spectacular. I have heard that Taste Pilots grill has good burgers.
If you can get to the hotels there is great food at the Storyyteller Cafe and Napa Rose(expensive) at the Grand Californian. Hook's Point and Goofy's Kitchen (character buffet) and Granville's Steakhouse (EXPENSIVE) at the DL hotel.
I have yet to try the restaurants at Downtown Disney but they are extremely convienient. I have read great reviews of Ralph Brennans.
Have loads of fun.