I have a friend who has severe life threaten allergies (fish, peanuts, to name a few). But over the years she has discovered that A) vegan organic restaurants are the best for her and B) she plans ahead when she is going, she will call ahead of time, talk to the chef, make arrangements with that chef so he/she is the one cooking and that they understand her requirements.
She doesn't eat out often, and its only super expensive places that will make these arrangements, but she has found a couple that are very accommodating.
In your shoes, I would recommend to check out the restaurant online, decide if you like the menu ect, then call, and book a light meal (maybe a soup or salad) at a time when the restaurant is not busy ( like a 3pm snack rather than a mid dinner rush at 6), and talk to the chef. Good luck!
"Of course its hard, if it were easy everyone would do it. Hard is what makes it great"
-League of Their Own