Seriously consider visiting Disneyland during the Holidays. Disneyland with all of the Christmas decorations up is simply Disneyland at its best. Plus, there's the excellent Small World Holiday and Haunted Mansion Holiday versions of those rides, and the Christmas version of the nightly fireworks with the snowfall finale'. Add in the Christmas Parade, stunningly beautiful decorations everywhere, and the usual seasonal cheer, and it's an amazing time to see Disneyland. They even have the White House Turkey who is pardoned by the President on display in the Big Thunder Ranch, and this past year they shipped in a dozen live reindeer from Alaska who lounged around the cabin where Santa Claus poses for pictures!
But beware, Disneyland has cornered the market on Christmas with SoCal locals, and the last two weeks of December, the Thanksgiving week, and any Saturday from mid November through early January is often the busiest days of the year for Disneyland. It is not at all unusual, especially those last two weeks of December and Thanksgiving weeekend, for Disneyland to shut its turnstiles and stop selling tickets by 10:30 or 11:00 AM each day. They did that for several consecutive days this past year during the week between Christmas and New Years and it always catches people off gaurd, especially when they are locked out and can't get in to the Park.
But if you can get to Disneyland in early December, and preferably on a weekday, you are guaranteed an amazing time at Disneyland.