The sorghum grains are fine. Numerically, they are sub par nutrition, but studies in developing countries show, again and again, that chickens can do quite well with sorghum in spite of its poor nutritional numbers up to a significant (>20%) part of the diet, for reasons unknown. Its speculated that sorghum provides certain enzymes that make nutrition of other ingredients more bioavailable.
I've deliberately planted both sorghum, and sorghum/sudangrass hybrid in my pasture for just that reason - without success, sadly.
Oh, and your chickens will nibble at the greens - mostly chasing bugs - but certainly not to excess unless you chicken tractor them over a patch and leave them w/o alternatives.
Don't sweat it.