The thing is, we eat at these luncheons maybe once every dozen or so occassions, so I am effectively imposing a diet on other people. I do it with good intentions, though, as well to alleviate some of my own guilt (as I said, I don’t want to be the impetus for others eating meat if I can help it).

Seems like you know the answer then. I think the pollution toll of actually feeding your staff is tolerable. Either way, you shouldn’t try and make everything about your beliefs do what you think would make the group happy.