Hi there, Anna, and welcome to planDisney!
Thank you so much for coming by with your question. I hope you're having a magical day and I'd be happy to help you with your inquiry!
Anna, per the
Terms and Conditions for the tickets you've purchased, I'm afraid that they are nonrefundable and may not be downgraded after purchase. Although that might not be what you were hoping to hear, I would encourage you to use those Park Hopper tickets to their fullest advantage! It's so easy to hop from one Park to another at the Disneyland Resort because the Esplanade is only a few Tiggerific bounces to get to the other side! You'll have the freedom of going from one Park to the other on a whim beginning at 11 a.m. Also, if you happen to be visiting Disney California Adventure on a Grad Nite, that Park will be closing early and you'll be able to continue the fun by hopping over to Disneyland Park.
However, if you know that you'll only be visiting one Park each day, another option would be to save these tickets for a future visit and purchase another set of one-park-per-day tickets. Even though tickets are nonrefundable, Disneyland Resort Theme Park Tickets generally have very long shelf lives. Even after they've expired, you can apply the price of wholly unused, expired tickets towards the purchase of new tickets as long as the price is equal or greater.
When you visit, be sure to take in all the decorations and
foods that are being offered as part of the
Disney100 Celebration! And don't miss the newest attraction in Mickey's Toontown,
Mickey & Minnie's Runaway Railway! It's a wonderful attraction for the whole family and you'll leave humming "Nothing Can Stop Us Now."
Anna, I hope that was helpful for you and that you have a fantastic visit to the Happiest Place on Earth soon! Please reach out to us again if you have any more questions! We'd be happy to help!
We'll See Ya Real Soon!
-Al