I wanted to let you know that I buy a liquid form of B12 from Pam Popper's Wellness Forum located in Columbus, Ohio. She is friends with Dr. McDougall and the other big names in the veg community.
I emailed Dr. Popper when my daughter was 20 months old about how much of the supplement I should give her. She emailed me back and recommended "one drop every few days."
I stopped nursing my child at 25 months, and I give her two or three drops of B12 on Sunday and Wednesday. I just talked to my pediatrician about this, and he was fine with this schedule. He was also happy with my daughter's growth and development, and he didn't have any problems with the vegan diet...
I have been afraid at times to talk to doctors about her foods, but I must say for the most part I haven't had too much criticism. I would try another doctor for sure if you are having troubles...
I think as parents we obviously want what is best for our kids, and it can be a bit frighting figuring all this stuff out. I'm finally starting to relax because my daughter is perfectly healthy, and the doctor was really happy with her....
Here is Pam Popper's email. You could try her with your questions, and she may be able to help you.
pampopper@msn.com