milk is nutrient dense and toddlers are picky eaters and sometimes dont eat much. even if they are good eaters it's hard to get all the nutrients they need in their diet.
i just went through a whole thing with BabyPunk looking at the various nutrients in each type of plant milk because she has eating issues.
there's this thread down a few threads discussing plant milkshttp://forum.theppk.com/viewtopic.php?f=10&t=34657
depending on what your kid is eating the nutrients you may want to look for are Vit D, calcium, protein, B12, and iron
i dont know why the article you found says not to give kids under 2 soy. i never did any research on that though. BP didnt eat anything til after she was 2 anyways.
personally i recommend soymilk for the younger ones it's got a crepe ton more protein than almond milk.
i thought almond milk was higher in calcium but when i was looking at the Silk brand both soy and almond had the same amount of calcium. i was trying to diversify what plant milk BP drank for awhile because she eats tons of soy yogurt but then i realized soy milk had much more nutrients in it which she needs because her eating is poor.
i also found that not all plantmilks are fortified with B12, in fact most of the ones available around here are not. all Silk plant milks except the cashew one for some reason seem to have B12 and Vit D2. people say that the Whole Foods brand of plant milks also have B12.
if you can get your kid to eat a vitamin then that helps a lot. there is discussion of vitamins in different threads on here including the one i posted above.
not sure if a 14 month old would be able to handle a vitamin yet but every kid is different (im talking about the mechanics of chewing and eating something hard not the actual vitamin itself). but my opinion on all things food related is skewed because BP struggles so much in this department.
if your kid is a good eater it becomes less important but it's kind of a safety net to get nutrients into them.
mollyjade has a great suggestion with Vegan for Life. it's a great all around book for any vegan and has really solid science based research in it