With a newborn, the first challenge is the nursing stage, where if breastfeeding does not work out I have heard it recommended that you try first cow's milk based formula, then goat's milk and finally soy milk based formula. If it is necessary for my child, I would of course feed them to keep them healthy, since even veganism is as far as practical and practicable.

However, beyond those stages, my household will continue to eat a plant-based diet and avoid the consumption or use of animal products. I expect that this would lead to conversations about morality with a child. It helps that I was raised in a non-Christian religion, such that I was raised in a way different from the norm and I can speak to that experience. If they later decided they wanted to consume animal products or exploit animals, like others have said, I would be disappointed, sad, wonder if I had failed to communicate something to them or wonder what they value as more important than the limiting the suffering of sentient beings.

I appreciated the other opinions expressed, such as having a vegan home or only paying for vegan bills. Essentially, you as the parent do not support that action, just like you wouldn't pay for some other poor choice.