We actually arrived at the party around 7:15, and from the crowds it seemed that people probably were able to enter some time before 7. There were people everywhere. From what I have read if you arrived before 7, they would direct you to Toontown. I can't confirm this. But I can say that there were signs stating that the park closes promptly at 6 (for those not at
MNSSHP). Also you were given wrist bands as soon as you entered.
As far as the rides/attractions...most of the more popular rides are open (buzz lightyear, splash mountain, space mountain, dumbo, it's a small world, PhilharMagic, etc), with little to no wait ! They did have a brochure for the evening outlining what rides/attractions are open. Of course they gave out candy, and had a Halloween parade, and special fireworks, all with the Halloween theme.
They did not show Wishes the night we went (Sunday); we did though get to see it on Sat night.
I must say, it was defintely worth the money, not only for the kids enjoyment of the candy, and parade, but there were virtually no lines for any of the attractions.
Enjoy
MVMCP !