Hello there, Ileene! Welcome to planDisney. It looks like you have a visit coming up rather quickly, so let's get you an answer to your question!
You most definitely can change theme park ticket reservations for Magic Key passes and for tickets if you decide you want to start at a different park than what you originally reserved. I would be happy to walk you through the steps to do that. Before we do that, I want to make sure to share that before you decide to cancel any reservation to make a new one whether it's for a different day or for just a different park, you should always look at the
Theme Park Reservation Availability Calendar for tickets and the
Magic Key Availability Calendar. This is because first you will need to cancel your reservations and then go through and make new reservations and it would be so sad if you canceled your reservations only to find out afterward that the reservations are full for that day now or the park.
To cancel the ticket or Magic Key pass, log into the appropriate Disney account. Then hover over "My Disneyland" and click on "
Ticket and Reservation Details". This will take you to a page where you will want to click on "View My Park Reservations". Then you will find a page where you can scroll down and view all of your upcoming plans for any ticket or pass linked to that account. From there, you will find the option to cancel a reservation to the right of each reservation. Click that and follow the process until you have confirmed your cancellation. Then you can go back in and book new reservations through the "Ticket and Reservation Details" page.
Ileene, I hope this is helpful to you. At the time of writing this, it looks like there is still some availability for that day. I hope you get it all sorted out. Please come back and see us again soon.
Carrie