And how to be even cooler gluten-free Christmas guest?

Well now, let`s see, that is something to consider...
Don`t be a drama queen and don`t roll your eyes if the hosts don`t know anything about celiac disease and gluten intolerances. They don`t know, so what? Do you know all the states in Africa or  Chilean yellow leech bite side effects? See, you have no clue. Be nice to your hosts and kindly explain your problem. Because you are the one who has the problem, not them.
Be cooperative. Offer to bring a gluten-free cake or freshly baked bread, for other guests to have a piece. It is more likely that this kind of gesture will help you feel less isolated. You`ll spread the consciousness about the celiac disease just by bringing some food and you will help the others to understand your problem. People will appreciate it, that is for sure.
Don`t come to the party starving and then faint in front of the entrance door. You are not Scarlett O`Hara in that legendary scene where she`s trying to squeeze herself in to that green dress. Snack before dinner or a party is a must!
Seriously, who are you cheating on? One of the most famous „perks“ of celiac disease is zero tolerance on cheating in your diet. The beast called celiac disease transforms to your loving friend only when there is no gluten present in your body.  Only 1/8 of tsp of gluten is enough to damage your intestines. Inflamed intestines will need 3-5 years to recover by persistent and disciplined diet. Forget about whiney excuses: „Oh, I`ll just take the cream part of the cake, I won’t touch the pastry. It`s Christmas, I deserve it, right?“ Or that miserable one: „So what, I`ll take just this one teeny tiny cookie. Nobody will ever find out.“ Slap yourself in front of the mirror to put yourself together. Somebody or something will find out. You and your body.
Don`t come to the party with a dark motive, such is a hidden USB stick in your pocket, containing PP presentation about the celiac disease. Seriously. When people ask you about celiac, they are just trying to be courteous. They don`t really want to know about every single aspect of intestinal problems or the details of the small intestine biopsy. All that during the Christmas party. They don`t.  So, beware of that one too many glass of wine that transforms  you into that medical presenter. That is, if you want to ever be invited to any kind of parties. Ever again.
Be open-minded and cool, but still, discreetly monitor how your food will be served to you. If you notice that someone is cutting the cake with gluten and the GF one, or is using the same serving spoon for all the dishes in the bar, don`t  sulk or freak out over it. Kindly explain to the host and suggest the way of fixing the problem.
Don`t forget to have fun  - sans gluten this Christmas!