We had a banquet event to attend this last weekend at the local Clarion hotel. For obvious reasons I usually cringe at the thought of such things. A couple of weeks before the event, we contacted the event coordinator. She, in turn, put us in touch with the chef. I have to admit that at first I was a little put off by "oh, we do gluten-free." There is a world of difference, the two are not interchangeable, and I don't like being dumped into that category. In reality though, everyone was very helpful with regards to menu items, their knowledge of ingredients and allergens.
Saturday night, my husband let the servers know that the food mutant was seated at table 23, they brought me my meal with only minor modifications from the event menu, and a good time was had by all. Desert would have been nice, but it's not like I need more sweets.
If you need a special accommodation don't be afraid to bring it up. No one will know you need something different if you don't tell them! Some places are very difficult to deal with, but some places, like the Clarion, are staffed with true food professionals and can be a pleasure to work with. Just be sure to let them know when they've done well. Too many places only hear about when someone is displeased so it is important to compliment a job well done.