Based on my experience from our trip during Columbus Day week last year, I would NOT advise planning to visit MK on Columbus Day. The crowds were Christmas-week crazy. We were there from Sun before Columbus Day to Sun after. As the week progressed, the crowds fell off.
My concern is that more school systems here in TN are taking the entire Columbus Day week off for Fall Break. Last year, the private schools took the whole week and the public schools took 2 days. This year, both private and public schools are taking the whole week off.