I'd be contacting this guy to see what he says, what he'd like to eat, it's the best way to tailor a diet.

If there's several folks who are not veggies then you may end up cooking two meals, one for him, one for others. I've done this for decades, so has my wife. We have a veggie daughter in law plus my stuff so it can get complicated at times. But you don't want complications in camp or on a boat if you can avoid it.

Beans and rice are always good and can be sauced or flavored in many, many ways. Try looking up vegan menus online. I have a lot of food allergies...don't ask, it ain't worth mentioning....and ate brown rice and red beans, black beans, pinto beans, etc. for three decades. Can no longer eat rice, but that's another page of the same story.

Cream of wheat, oatmeal, cream of buckwheat all are good bases but IMHO lack a complete protein. A word that you might look up is "complementarity" as it relates to food, the mixing of this veggie thing and that to make complete protein. So Soy? Is it ok? If so, soy has good protein to mix with things that lack complete protein. Hemp hearts are a great way to get a lot of protein sprinkled atop the aforementioned cream of......whatevers that lack some protein.

Hope this helps to point you in a good direction.