If you want to grab something kind of quick - there's a coffee shop at the DLH that also sells pastries, I believe. It's by Goofy's Kitchen.
If you want to grab something on the way to Disneyland, then you can try Compass Books - we usually just grab something there, plus they have milk if you want that instead of coffee. Jazz Kitchen Express window and La Brea Bakery are also options you can try. I've had oatmeal at La Brea Bakery, and there are other options there to try.
Inside Disneyland try the bakery on Main Street or Carnation Cafe.
Have a great time!