"(I've resolved that if any of my children ever want to be vegetarians, I'm OK with that, but a critical precondition is that they demonstrate that they have do

"(I've resolved that if any of my children ever want to be vegetarians, I'm OK with that, but a critical precondition is that they demonstrate that they have done their homework and understand the nutritional implications. I believe it can be done safely, but it's not trivial; it takes work in our environment.)" You legitimately have a point that there are certain nutritional deficiencies that vegans/vegetarians are more prone to. That said, I would hope that whether or not the child is a vegan, you would have him understand the nutritional implications of what he is eating. Being an omnivore safely is also quite difficult.