A Vegan diet is not recommended for babies. There are many things which could go wrong and lead to delayed development.  Please only do this while closely  consulting a doctor with regular checks. Also you should at least breast feed till the age of 2 and take supplements of vitamin D and B12:h
https://www.ncbi.nlm.nih.gov/pubmed/10966896
http://www.nytimes.com/roomfordebate/2012/04/17/is-veganism-good-for-everyone/a-choice-with-definite-risks