Hi Beth!
Halloween time at Disneyland parks is a really special time and they go all out to make it exciting and fun for all the guests. Personally, I think Disneyland does it a little bit better as they actually transform several of their rides into Halloween themed attractions for the duration of the holiday season. It gives the guests a new and different perspective of an older ride so its fun to come and ride them again and again.
In the past years Disneyland park has had at least 23 of their attractions open and running during the party. This includes rides that appeal to all ages from the thrill roller coasters to the Toon Town attractions. Of course until the party starts we will not know exactly what will be open each party night.
This year the addition of the California Adventure Park is really exciting news. The Disney parks blog has a great
Article about some of the new changes coming in 2017. We know that Cars Land and Buena Vista Street will be decked out in holiday splendor but so far they have not officially given a list of attractions that will be open. I can imagine it will be similar to the Disneyland Park and there will be most, if not all, things operating in California Adventure.
I know you will have a great time that night. Don't forget you get to arrive three hours early to enjoy the park before the party starts. And don't miss the Headless Horseman who was added to Disneyland last year. It is a great night of fun and lots of treats and few tricks!