In a short answer yes.
The long answer.....it would depend on how it was presented and implemented. I don't think it's a given you are automatically healthier if you are vegan; we see plenty of unhealthy vegans. Remember, veganism is a way of life, a philosophy that strives to reduce animal suffering and deaths. So that can be implemented in a myriad of different ways, some better for your health, some bad for your health and some inconsequential to your health.
I think being a vegan child would lead to being more emotionally healthy. But if there is a backlash from other children, then that might offset that gain.
My friend is vegan and has been for 7 years, her youngest were both raised vegan from birth, and the eldest was about 3 when the parents became vegan. 7 years later her kids are fine. My other friend has kids raised as vegan from birth. They are also healthy and fine no health issues related to diet for the past 10 years.
My own children are I think too old for me to put veganism "on them". They need to make their own decision as I think it would greatly increase their anxiety levels to a degree detrimental for their health. Given their limited diet anyway (fussy eaters) a vegan diet would essentially be an almost starvation diet unless I constantly gave them vegan chocolate cupcakes.
The only society that I can find that is traditionally vegan are those that follow the Jain religion, and plenty of them seem to grow up to adulthood? but I could be misinformed.
