both... but if you have to chose, I'd go the first week of December. All of the Chrismtas decorations are up and the parks aren't that crowded that week. We've gone that week for the past 4 years and LOVE it! The weather is usually great and it gets you into the holiday spirit for sure Although, if you can try to get there for Halloween too as it's a lot of fun as well. The Not So Scary Halloween Party is tons of fun! HTH!!
Oh, also we did MNSSHP and plan to do MVMCP. We found the Halloween parade to be a bit scary for our the 3 year old and even for the then almost 7 year old. I think we'll be safe at Christmas time!