As I recall - the MK closes around 6pm, if one has the ticket to the
MNSSHP and enters after 4pm one can get a wrist band. There are many places through out the park to get them, just show the ticket if you are already in the park. If you enter after 4pm you will be banded as you enter in front of the train station before you go under the overpass/tracks.
We like to make a dinner reservation for a sit down restaurant for about 530pm, this way the crowd is thinned out before we head out to play.
The party officially starts at 7pm. At the banding stations and at each "trick or treat" station the cast have bags (for loot!) and maps of the "candy stations" where you get to go trick or treating!
Most of the rides were open as I recall. I do think that Big Thunder Mountain is open.
Many of the villian characters are out and about - be sure to get a good location for the parade. Be lined up at least 30 minutes prior if you want to get a good picture of the head-less horseman. I have found that standing at the bridge by the castle, on the side across from the funnel cake place is a great location. One gets a full face view of the horseman, is protected from the push of the crowd, and the horseman stops at the VIP station on the other side of the bridge. He is amazing. Running through the park in the dark on a horse with no head (the rider really can't see - the horse is trained I have been told...)