Very hard to get ADRs, but I have always managed to get in somewhere. Usually at DTD. But I have never tried at the 180 day mark. Maybe you have better luck at the point at getting into one of the more popular resort restaurants. We have eaten at Kona Cafe, Rainforest Cafe, and the Whispering Canyon. We always had members of our family meet us who did not have park tickets, so we ate outside of parks.
MK was particularly crowded on T-giving day, but we are early risers and get to the park at opening or choose parks with early entry. If it gets too crowded after lunch, we head back to the resort or over to DTD. We have always managed to ride everything that we wanted to on our T-giving trips without too much wait.
You will have a great time! Wish we were going back this T-giving!