Greetings Lupita!
A September trip to the Happiest Place on Earth promises to be both Magical and full of Fall-themed decorations!
During the month of September,
Mickey's Halloween Party nights are on Wednesdays and Fridays.
However, since you've indicated you'll be making a trip on
September 19, your Park experience will not be affected because the first day of Mickey's Halloween Party is not until the next day, Wednesday, September 20!
That means that guests who are visiting the Disneyland Park on September 19 (like you) will be able to stay until regular Park closing, which is scheduled for 9pm.
I'm not sure how long you're staying at the
Disneyland Resort but it may not be a bad idea to consider purchasing a ticket for the Spooktacular festivity.
There are still Mickey's Halloween Party tickets available for September 20 and I promise you'll have tons of fun!
I hope I've answered your question.
Thanks for visiting the Disney Parks Moms Panel!
-Anabel M.