i went on the disney magic cruise last year nov. 11-18th. When we arrived on the ship there were no decorations and we liked that because the last times we went on the wonder was over christmas, and the last time we went to disney world it was over christmas so we wanted one vacation with no holiday decorations.
So we went to bed that night, and when we woke up EVERYTHING was up. Christmas tree, garland on the railings, EVERYTHING. call it disney "magic".
But it was beautiful, so we really didnt care!
So that was november 12th. I'm assuming the theme parks work with the disney cruises time schedules too, but i could be wrong!