My wife has Celiac- so I have some idea what you're dealing with (especially since I do 90% of the cooking in my house). Not the easiest career to have with your disease.
I'm guessing you're never going to be able to reliably get GF meals- especially when you have any sort of last minute schedule change. I would get a letter from your doctor stating that you have Celiac, take it to your base CP, and just ask for reimbursement for meals when they are due to you. I'm guessing they won't give you any hassle about it.
Now, actually getting reimbursed from AA...