...did I say the volume needed was so great? If I did, what I meant to say was: the volume yielded in a home garden is NOT so great, which is one reason why most people buy their whole grains. Maybe amaranth would be possible to harvest enough to cook for your family, but in general I think most grains are store-bought. Grasses are definitely a popular favorite to grow in home gardens for ornamental use though.
Sorghum is one of my favorite whole grains. Sorghum seeds germinate pretty easy. Seeds can be popped like popcorn too. And, it's gluten-free (like rice) for individuals who can not tolerate gluten. You can buy sorghum flour for use in baking. Here is a link with more information about sorghum: