[user104658]

TBH I find there's a lot of idealism from people who haven't actually had children, when it comes to children and veganism.

Most children forced onto a vegan diet end up with an iron deficiency, or even anemia. This is what is causing the pale skin and lethargy. Now, this is where vegans start crowing about how many other sources of food, such as green veg, contain plentiful iron to replace the loss from not eating meat.

I challenge you to try to get a child to actually eat green veg. Most children simply will not eat enough of it to replace the iron source lost from not eating meat. They'll load up on grain-based carbs and fruit no problem. They're not going to eat brocolli. It just isn't going to magically happen. "Oh but if that's what they're used to getting" blah blah blah NO... the people saying this are almost exclusively childless and are talking ****. Or they're the vegan mummies pretending that their pale, lethargic child does indeed eat all of his green veg. Spoiler: He doesn't really.

tl;dr I think it's a perfectly acceptable, great even, diet for adults but until there are genuine replacement products that children will actually reliably eat that contain the lost essentials... it is a selfish and dangerous decision to make for a child. Humans are omnivores by nature. It may be more morally correct to be herbivore and with a varied diet it is totally possible but, no, it is not natural; it is a decision, and decisions are for individuals to make, not for parents to force upon their children. Let them eat a natural, varied human diet until they are old enough to make the decision themselves and then by all means encourage it... when they are old enough to understand nutrition and why it's important to eat the "yucky parts".