We adopted 4 ADD ADHD children and at first I too had this ideal that we could handle things just fine without medications (for them, not us :) ) however even though we homeschool we've been educated on the medication and why it's needed.
Their meds allow them to FOCUS and CONCENTRATE! Without them they were prone to destructive behaviors such as not looking both ways before crossing a street, unsafe bike riding and risky behaviors way beyond their capabilities.
Having your grandson evaluated by a "competent" medical person is your first step. There are several tests (I prefer the TOVA)that will tell if he is truely ADHD or simply high-spirited. If he IS ADHD and needs meds now that doesn't mean it's a lifelong sentence. It will merely give him the confidance to finish a project and stay focused long enough to learn without being disruptive to himself and those around him. Good luck.