Under some circumstances that is the only viable solution but often an imperfect one. The BB is ballistically unstable in flight and thus inherently inaccurate. It does have awful bounce characteristics and the old tale about shooting one's eye out is unfortunately based in fact. Where I had a choice when a "real" firearm wasn't available I would go with a .177 air gun or a .22 airgun that was pump operated instead of the old style spring driven BB. But it is incontestable that you have to work with what ya got not what you wish you had. I'm glad you were able to impart the basics safely with the venerable BB.
He did pretty well, I'd say.
I watched one of his daughters blasting coke cans and water bottles with a Ruger 10/22 a few weeks ago.
I saw very little to criticize.