We routinely teach with one of these Bobcats and our minimum age, is 11. I chose the Bobcat because it's so light and easy for the kids to shoot. Kind of depends on your powder. When we taught with Pyrodex, we were teaching with 40 and 50 grains. We now have gone to 777 and have cut back to 40 grains. I would not have a problem with
30grains of 777 or Pyrodex, for your Grandson. You have to be careful not to go too low. You want a little bit of a bite but not to hurt the kids. We also teach adults in these classes and this load suits them as well. You might want to consider putting one of those slip-on recoild pads on the Bobcat as plastic one, provided, stinks. I compliment you on the time you are spending with your Grandson. I'm am curretly working with my #3 and he can now load and shoot with little supervision, at 12 years of age.
You get my; Atta-Boy and:
Be Safe !!!