Don't know if this will help anyone, but I've had the discussion (once) with family (in-laws and out-laws) that this isn't a "fad" diet, and it's not like choosing to be a vegetarian. It's a serious autoimmune disease that can lead to MS, Lupus, Cancer, Diabetes, GERD, Thyroid problems, and more. (I'm pretty sure Parkinson's Disease, but haven't seen any literature supporting that.) If there's a family history of those diseases, I've mentioned them by name, some of whom are dearly departed. First cousin Connie, MS, mother, two aunts, breast CA, etc.
I love my family, as we all do, and I love the things they cook, but I have to be super careful, as you do, about what I eat so that I can live my life as normally as possible.
Now they (the family) pretty much leave me alone on the food front. They don't make a big deal about what I will or won't eat at get-togethers, and I don't either. It's not about food. I bring my own food (with something to share) or eat before the event so I don't get sick.
My sister still tries to buy special things for me at parties at her house. Even though she's super smart, she bought me rice crackers for her last party and pointed them out to me. I told her I suspected they had soy in them. She hotly retorted that she'd read every ingredient and there wasn't anything I couldn't have: gluten, soy or dairy. I asked her to produce the package and sure enough, there was soy listed in the ingredients. I told her how much it meant to me that she went out of her way for me.
If she couldn't have produced the package, I wouldn't have eaten them anyway. It just isn't worth it. But I was genuinely grateful to her for trying. My sister wouldn't knowingly poison me, we love each other to bits.
So don't get pressured into eating what those who love you want to cook for you, unless you really trust their knowledge. Holidays and celebrations are not about what we stick in our mouth. If our relatives can't get that, then they have a bigger problem than we do.