Mike,
One of my children was sculpting and drawing recognizable faces and figures at age 4. (I am allowed to brag)
I would say from 9 or 10 is as young as I like to teach, and only then in half hour classes and no more than 6 to a class. I would think that with your studio set up, if you have room, you could have a very select group of talented kids who would appreciate the opportunity to learn, and you in turn will derive a great deal of pleasure from them. Not, however, if it turns into babysitting.
They need pencils and drawing pads, nothing that makes a mess. All you should need to do is set up the subject and give assistance as required. I try not to mix high school and primary school ages but if they are well behaved (and they don't come again if they are not) mixing ages is OK.
I also found that telling them a very descriptive short story and then getting them to illustrate it was a great way to inspire creativity. I also have found, in general, that the truly talented child artist is also a talented dancer or musician or writer or sportsperson with many commitments and they love the quiet time of a drawing class.