Hey there Bek,
Welcome to planDisney and thanks so much for your question! It sounds like you're planning a frightfully fun visit to the Disneyland Resort that will be here before you know it!
The event you're seeing on select evenings during your visit is called
Oogie Boogie Bash - A Disney Halloween Party, and while tickets for this event are sold out, fear not! There is still plenty of
Halloween fun to be had around the Disneyland Resort, which I'll cover more in-depth below.
As for how it will work on nights that have this special event during your visit, Disney California Adventure Park will close at 6:00PM, but you can use your Park Hopper ticket to spend the evening in Disneyland Park instead! I'm not sure how long you'll be visiting, but this special event will be occurring on September 10, 12, and 14.
The way I would recommend planning around this is to make a
theme park reservation for Disney California Adventure Park for that day. You can spend the day exploring the Halloween offerings in this park like
Guardians of the Galaxy - Monsters After Dark and see Cars Land all decked out as "
Radiator Screams."
Then when this park closes, you can hop over to Disneyland Park to enjoy the evening by taking an photo in front of the iconic
Mickey pumpkin, riding through
Haunted Mansion Holiday, and catching the nighttime spectacular
Halloween Screams.
Additionally, I'd recommend keeping an eye on the
Disney Parks Blog for more articles on fun things happening around the Disneyland Resort, and watch for a special
Foodie Guide that should be coming soon that will cover all the delicious items to eat and drink around the parks as well.
Thanks again for your question, Bek! I hope you have a fantastic visit to the Happiest Place on Earth!
Have a Magical Day,
Greg