Hey, Jacqueline! Welcome to planDisney.
Oh, bother! I'm so sorry that you've accidentally purchased the wrong
ticket for your 11-year-old. As you've discovered, tickets for Guests 3-9 are slightly cheaper than tickets for Guests 10+. Since your child is 11 years old, they would be required to have a ticket that matched their age. Unfortunately, once purchased, tickets are non-refundable. However, you'll be pleased to know that theme park tickets never lose their value. Even if they expire, you can always apply their value to the purchase of new tickets. I know that's not the answer you were hoping for, Jacqueline. You can always call
"Existing Tickets" and speak with a Cast Member to see if there's anything they can do about your situation. However, the official policy is that tickets are non-refundable. I will say that Disney doesn't require children to carry ID in order to enter the parks. Guests are expected to adhere to these rules using an honor system.
I'm sure you and your family will have a truly wonderful time, Jacqueline. There are so many fantastic family-friendly attractions, such as
Mickey & Minnie's Runaway Railway at Disney's Hollywood Studios,
Remy's Ratatouille Adventure and
Guardians of the Galaxy: Cosmic Rewind at EPCOT,
Kilimanjaro Safaris at Disney's Animal Kingdom Theme Park, and
Seven Dwarfs Mine Train at Magic Kingdom Park. Enjoy every magical moment!
Mike