Most of the rides are open. Last year Jungle Cruise and Hall of Presidents were closed. I'm sure there were a few others, but most are open.
Ride lines are generally short on any party night, even on a sold out night.
Do keep in mind lines for characters can be long and room to watch fireworks tends to be very much in demand. These are the things most people go to the parties for so they bog down on busier party nights.