Google Scholar has lots of studies, here are a few:
http://www.ajcn.org/content/48/3/822.short
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-277X.1992.tb00129.x/abstract
http://pedsinreview.aappublications.org/content/25/5/174.short
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2656635/
From the reading I've done, I've found mixed results on height (some say vegan children tend to be taller, others say they tend to be shorter)... I think this is more a genetic thing (in the absence of severe malnutrition or growth hormone issues, that is). I don't really care what height my kids are, TBH, so it's not something I've really looked into much.
In terms of overall health, the studies seem to indicate that most vegan children are very healthy. I think you just need to be smart about it... both vegan & non-vegan kids will have various deficiencies if they are eating a limited diet and are not supplemented accordingly. I do have to say I'm uncertain about comparing vegan blood levels with the population at large, since most of the comparison population is not vegan. It would be nice if there were vegan standards of blood levels that take into account how differently the body utilizes vegan & non-vegan sources of nutrients. Some vegan children will have low levels of iron, for example, but not be even slightly anemic... so I would argue that if they aren't experiencing any negative health effects, their low iron levels are 'normal' (for a vegan child).
The only things I've read about IQ are what you read, that people with higher IQs are more likely to become vegetarian.
Anecdotally, my 3yo vegan DS (vegan since conception) is really short -- however DH & I (and our parents, too) are also really short. He seems healthy overall, is rarely sick. He had a minor neurological issue (a tic, probably due to anxiety) for a month or so once, and has high anxiety overall (but again, virtually everyone on my side of the family has major anxiety disorders, and none of them are vegan or were as children). He is very smart, when evaluated for EI at 2yo for some social/emotional issues, he tested at 4yo level (the highest they test) in nearly all areas. He is also an amazing eater... he will eat just about anything and really loves his veggies. I don't know if that's due to being vegan, or doing baby-led weaning, or we just lucked out, but he eats so healthily and so well, so I feel like the vegan diet is a good fit for him for now.
. I got it out from the local library. It will not have the most recent studies, but it goes through every study up until that point and reviews each study in a non-cheerleader way.
