We went for our first time in October last year. The first few days was HOT and HUMID, but the crowds were definatley manageable. Then Wilma hit and a cold front came through and it was actually on the chilly side for our last 6 days.
October is a beautiful time to go, but since we are from the far North, the heat and humidity were hard on us so we probably would not go again.
MNNSHP was great! We loved it. My son got som much candy and our main priority was not even trick or treating.
They supply you with the treat bags and the parade and fireworks are awesome.