Hubby and I are both veggo's, but not vegans. By default, our kids have been pretty much raised as veggo's. If they go out somewhere, or to someones house, I don't insist that they refrain from eating meat as I think it's important for them to make their own choices, but I do find that they will often reject the meat options anyway.

My kids are healthy and happy and don't get sick any more often than their meat eating friends and they have heaps of energy and have never suffered from anemia or fatigue.

As long as kids have a healthy, balanced diet, I don't think being veg is an issue.