Hi there, Merary!
Thanks for visiting planDisney! I still have fond memories of visiting Disney Parks with my friends in high school, I'm glad that your son will have the chance to experience the parks with his pals.
Yes!
Disney Gift Cards are currently accepted at restaurants in the parks and most food carts are able to accept them as well. It's always a good idea to ask before you order, just to couple check. You can also use a Disney Gift Card as a payment method in the
Disneyland Mobile App. The app won't remember the card number between purchases, but I like to make a note in my phone with the card number so I can easily copy and paste it when I'm placing a mobile order.
If your son likes fun treats you should show him the Disney Eats Foodie Guides! Right now I'd recommend
checking this guide for Pixar Fest to see the latest and greatest snacks at the parks. I especially love the Eye Scream Cone inspired by Mike from Monsters Inc. at Gibson Girl Ice Cream Parlor in Disneyland Park. It's frighteningly cute! There's also a special churro available in Tomorrowland, since you mentioned churro carts specifically. A churro (or two) is always a good choice!
I hope your son has the best time with his friends, Merary!
Keep moving forward!
Amanda