Thanksgiving week will be insane.
We were there last year (leaving the Monday before Thanksgiving). The days leading up to Thanksgiving week were progressively more busy, but totally manageable. Then Monday happened! Although the kids and I arrived at rope drop at the MK (8am EMH) and got into the park without any trouble, by the time we left MK (just two hours later, around 10am), the crowd was the most insane thing I'd ever seen. Main Street was wall-to-wall people. Once outside the gate, we had to literally lock arms to stay together (since we were going the opposite direction from everyone else) and fight our way through crowds of thousands, just to get to the bus depots (and the crowd waiting for bag check was backed-up past the monorail line, half-way to the buses -- the monorail and boat loading areas were completely jammed, with security guards and CMs trying desperately to find places to move people sideways toward the buses, as there was nowhere for guests to go once they got off the monorail/boat). You could not have paid me to stay any longer over that week, and I'd choose any other time (save Christmas or Easter) to visit if it was between that week and another.