L.W.
My son is also 14 months, and I give him regular oatmeal now. No more baby anything for us. He eats what we eat. You can keep them on baby cereal/oatmeal as long as you want, but if you are worried about the vitamins, I wouldn't worry about it, if he is getting an adequate amount of fruits, veggies, grains etc. he is getting his vitamins. I had the same concerns as you.