If you give it to them and prepare it for them, it isn't their choice though. You're making the choice for them. If anything wouldn't it be more ideal to have the baseline be a veg diet and let them choose IF they want to eat animals?
I wouldn't ask my child to. In my opinion your kid should be able to choose, especially since not all your family members are vegan. It would likely seem unfair if you forced it on her, and as a vegan myself I'd hate for this decision to be viewed in negative light. YMMV, of course.
See I don't see raising kids to be vegan as any different than raising them with your own religious beliefs. When you believe that something is right and ethical, you teach that to your children and hope they learn to see the whys and hows, and choose that path for themselves as they grow older. Of course it's tricky. It's tricky to navigate with religion as well. But when you feel passionately about something, I think it's perfectly fine to pass that passion, and in this case, compassion, for animals and all life, down to your children.
My DH and I are vegan and both of our children are being raised the same. No exceptions as they are still very young (4 and 1). I do think it's going to get harder as they get older, and venture out into the world themselves. That's why teaching them the compassion part and ethics of veganism is so important. Marsupial - I think the idea of visiting farm sanctuaries is a wonderful idea. I'm going to start doing that with my children as well.
OP - honestly I just explain why we make these choices. Some people drink cows milk, we don't. Some people eat animals, we don't. My DD is starting to get more curious and my answers are getting a little more complex these days, but the heart of the answer is the same. We just don't believe it is right to use animals for food. We have plenty of other healthy things to eat, so we choose to eat those things instead.