Hello, Lydia, and welcome to planDisney!
I'm so sorry to hear that you will miss out on a fun day at the Disneyland Resort. But I am happy to let you know that your son's friend will be able to use your ticket instead. There's no need to change the name on your ticket because when your son and his friend arrive at the park entrance turnstiles, they will have their pictures taken and the tickets will be assigned to them from that point on.
It sounds like you already have theme park reservations set up, so your son and his friend are ready to go! If you purchased Park Hopper tickets, let them know that they can hop to the other park starting at 1:00 p.m. Additionally, it will be really important that one or both of them download the
Disneyland mobile app and link their tickets to the app. They can use the app to check attraction wait times, use mobile food ordering, and join the virtual queues for
WEB SLINGERS: A Spider-Man Adventure and
Star Wars: Rise of the Resistance.
I hope your son and his friend have a super fun time at the Disneyland Resort!
-Linda