Parties and restaurants? No problem!
My mom's house? Yeah, that can be a problem. She's very much into whole grains and low-fat everything. And she's happiest when she makes you a sandwich for lunch with brownies for dessert.
Last time I solved it by spending a lot of time with her, but staying at a hotel. We used the excuse that The Boyfriend and I didn't want to be living in sin at her house. Just being respectful, you know.
I've already got problems with sulfites (anything cooked or marinated in wine), sodium nitrite (pretty much processed/preserved meat) and she's seen me do Atkins years ago, so she is used to me saying "Eat whatever you want and I'll find something for myself".
If you are open about it, and also open to finding your own food to eat without expecting anyone to go out of their way for you, it usually works out just fine. If people ask, you can explain that you realized gluten was causing you problems. They might ask more questions, or they might not. Go with whatever curiosity level they have, but make sure you act matter of fact.
With my mom, it's a lot easier now than it used to be. I just tell her I'm trying to avoid the huge number of gastric issue that she and my brother have had over the years.