I appreciate all the advice. I learned some things here like the difference between a vegan and a vegetarian (didn't know there was) and the various points of view were interesting.

What I did was have a sit down with my son last night. I admitted to him that although I was the camp cook I was out of my element (thanks Mary Lou). There were several good (I think) suggestions of meat/protein alternatives posted here, however I have no idea where to find such things are what to actually do with them. What we ended up with is pretty much a meld of your suggestions. I'm going to bring and cook what I normally do plus a few extra pizza shells. FIL is going to bring some of his own veggie stuff. Son is more familiar with FIL eating habits so is going to bring related food.

In the end, as you all said, everyone is there to have a good time. If FIL chooses to, the standard camp food will be available. If not, he should be covered. Everyone drinks beer, so all should be good.

I really appreciate the time and input to a non-sailing post here.