My last trip, this past Oct/Nov, was planned around Halloween activities (my favorite Holiday).
At PI, there's a costume contest for all. It's great fun to see all the very creative things people come up with. There are big prizes too. PI was packed after about 10pm on Halloween night.
I also went to Universal's Halloween Horror Night on 10/30. If you love horror movies and scary haunted houses, this is the place for you. They have everything from chainsaw welding freaks in the streets to a goulish parade. This is a special ticket event and buy them in advance.
I missed the
MNSSHP at the MK but heard that it's quite a bit of fun, especially for families. The decorations are great too (saw those during the day). Again, buy tickets in advance if you plan to go. It was a sellout and many people left disappointed because they could not get tickets even days before (I tried).