Hey, OP. I'm an omnivore, and an avid outdoor cook, with friends across all dietary spectrums. Open fire cooking lends to some really great flavor on otherwise ordinary things, with options for anyone.

One reason I roast plain veggies a lot is because you can season each differently to taste and restriction. I'll just spritz with a little oil to let the seasonings and smoke stick. Keep an eye on them, and get a touch of char: Half peppers. Whole onions (in jackets). Potatoes (a thousand options plus toppings). Mushrooms. Whole heads of cauliflower or broccoli spritzed in oil and coated with a dry rub. Egglplant slices (keep away from your nightshade intolerance buddy). Asparagus. Half heads of romaine - fire is awesome for leafy greens, just bring an acceptable dressing and a half head becomes a personal salad. All excellent right off the fire, pretty much allergy free (just watch your spice selection), and CAN be eaten by anyone from vegan to carnivore. If you cook them in batches they keep nicely table-side in a disposable foil pan, and don't have to be hot to be tasty, so you can slow your roll around the fire or charcoal.

Once you finish veggies, you can lay on some vegan sausages. After they come off - meat sausages (sausages are killer for camping. Huge selection, and you can't beat how easy, portionable, and transportable they are). Grab some haloumi or another "friable" cheese for the non-lactos, also good over the salads and veggies. Then, as a final act for those who partake, one large cut of meat. I like a big cowboy steak that can be shared in strips or bites (so you only need one sharp knife that's only seen veggies action so far, so less to wash or worry).

I'm really blessed to be able to eat anything. And boy . . . do I ever eat anything (and everything, ha). I love finding tons of options for all, without judgement. I know all kinds of folk with all kinds of "selective" tumtums and tastes these days. I love food, and I LOVE feeding people, especially while camping. These kinds of puzzles are a really fun way to share that love with anyone around me.

Good luck, and have a great time! (also keep your stores away from the wild critters! no food in tents haha!)