Infants can thrive by being clothed, fed, and taken care of without the use of any non-human animal products.
An infant's ideal food in all but a few cases is human breast milk.
If the parents cannot or wish not to breastfeed the infant, the infant can thrive on soy based infant formulas, but no easily available infant formula exists on the market yet.
Once the child starts to consume solid foods, vegan foods can easily allow a child to thrive. The main concern should be a balanced diet with plenty of calories, espeically from fats. This is easy if the vegan parent prepares foods with flax or olive oils, plenty of greens, and nuts.