I think if you look at past year's you'll get a good idea of when they hold the MVMCP. I think it usually ends prior to the start of the "Holiday Season" resort pricing. This year Holiday Season begins on 12/20. Maybe someone here can give you the dates from this past year to use as a guide.
Last month they were Sunday, Tuesday, Thursday & Friday from Dec 1 to Dec 20. We went on a Tuesday night (Dec 10) and it wasn't real crowded. Fridays usually sellout in advance.
This year the last party was on Friday night before Christmas. I think they usually start the Christmas parade as the daytime parade on the Saturday before Christmas (and that parade only moves to daytime after the parties are over).