Yes, it should be no trouble. If you've already booked the lunch, call back and add dietary requests so they know in advance. I requested a vegetarian meal when I reserved the lunch and was accommodated with no problems at all. It was on my reservation when I showed up, and the chef gave me a separate vegetarian meal and replaced one of the dessert items that contains gelatin.
I would imagine it's not a problem to have the shrimp dish replaced for your meal, either. We requested that due to a possible shrimp allergy and it was modified... I don't remember what he got instead, I think it was something in a fish sauce. Chef David also modified one of the desserts due to a nut allergy. He was great and super nice, so I wouldn't think there would be any problems. But, even if there was an issue, you won't leave hungry. We were all so full by the end of lunch, and the shrimp dish is just one of 3 sampler items during the hot entree portion. The table shares 2 platters of the naan bread service with all the sauces. Then everyone gets a sampler of 3 salads, then 3 entrees, then 3 mini desserts.