Hi there, Jason!
As you might imagine, the chefs at Disney's restaurants, from the most elegant to the quickest casual, are well-versed in the art of improvisation. And absolutely, your chef at
Disney's California Grill will be able to work with you when you arrive.
You might want to call (407) WDW-DINE in advance, and have a notation added to your reservation that you'll need to speak with the chef about food issues. This might hasten the process. When you are seated, be sure to tell your server right away that you request a meeting with the chef, too.
When s/he comes out, you can offer some favorites based on the menu: you like pasta, chicken, etc. From there, you and the chef will be able to arrange a delicious meal just for you.
And don't underestimate the power of the children's menu. While it might sound funny, this is often a very good start for choosier eaters, and serve as a foundation for a very nice, palate-pleasing adult meal.
Have a wonderful time!
See you later, celebrator,
-Deborah B.