I have about a month to figure out what PS or ADR to make. I have never been in the fall or at Christmas time. Do these special ticket events effect crowd levels at the other parks or the next morning???
I don't think you have anything to worry about. Since this is a hard ticket affair and people must pay extra to stay/enter the MK, it probably won't affect the crowds. I was over there one afternoon last October and saw kids and adults alike coming into the MK dressed in costumes. Some were really cute and others funny. We passed a group of teenagers dressed as the cast of Gilligan's Island. They looked really cool but the Skipper was too skinny!