I can't give any experience-based advice on raising vegan children, as I have yet to produce any minature grasshoppers. However, as I do plan to do this in the future and have been looking for information, I can tell you about some blogs and websites that might be useful.
Our Vegan Pregnancy - this couple don't update a whole lot any more because they're busy raising the twin boys who resulted from the eponymous pregnancy. But the archives are still there.
Baby Steps Vegan didn't intend for her children to join her vegan journey, but they seem to have done so. Read her blog to find out what she feeds them and how she deals with potentially awkward situations.
The Vegan Society's parenting page has links to various resources.
ActiVeg has a similar page, inspired by Sophie's own experience raising two healthy vegan daughters.