These are the dates that I found in the AllEars newsletter, I hope I am allowed to post this. I called Disney and they said they haven't been announced yet, but it should be anyday now.
Seasonal Parties Announced:
-- Mickey's Not-So-Scary Halloween Party allows guests to trick-or-treat while immersed in the fantasy of the Magic Kingdom. The evening includes Mickey's "Boo-to-You" Halloween Parade; trick-or-treating throughout the Magic Kingdom at numerous locations; and the special Happy HalloWishes fireworks. Lots of characters are out in the park, wearing their favorite costumes -- you're encouraged to wear yours too. 2010 party dates and times are: September 14, 18, 21, 23, 25, 28, 30; October 1, 3, 7, 8, 11, 12, 14, 17, 19, 21, 22, 24, 26, 28, 29, and 31; November 1. The party runs from 7 p.m. to midnight; Mickey's "Boo-to-You" Halloween Parade is at 8:15 and 10:30 p.m. with the Happy HalloWishes fireworks at 9:30 p.m. Prices for the party are as follows (all prices listed include tax):
Advance Purchase: $57.46 for adults 10 and older / $51.07 for ages 3-9 (Not available all dates)
Passholder and DVC Member Discounts: $53.20 / $46.81 (Not available December 7, 10 through 19)
Day of Event (if still available): $63.85 /$57.46
http://allears.net/tp/mk/mnssh.htm