Christmas stuff should be up by Veterans Day weekend. We've done Vet. weekend before, and it is busy! Fine by Tuesday, but the 3 day weekend is packed. MIdweek things slow down some, pick up again on Sat and Sunday before Thanksgiving, slow some Mon-Wed. of Thanksgiving week, busy Thanksgiving, and avoid the park the day after Thanksgiving. We've done T-week every year since 2001, and every year it gets busier. Most of the schools in that area are out the entire Thanksgiving week, so that adds to the crowds - locals visit the park along with all of their out of town relatives that came for THanksgiving dinner.
Does this stop us? No.... we just go with the mindset of crowds of people, and lines of 30 minutes for the good rides (fastpass the great attractions). Fastpasses will likely be all gone by noon. If the crowds are too bad, we see shows and go to CA Adventure. It's still a great family vacation... and we always run into people we know while we're there.