I'm not an expert by any means, but I want to make a few points.
a 10 year old isn't an adult by any stretch of the imagination, and it isn't his responsibility to defend himself until he's of an older age. That's my opinion, we're required to feed, cloth and protect our children until they're old enough to be adults....
I'd leave a 12 gauge with my wife before I'd leave a .22 with my 10 year old. No matter how mature he is, he may end up making a mistake. Remember, at the age of 10 responsibility doesn't mean the same thing as it does to an adult.
Honestly, I have met quite a few grown men that shouldn't own guns at all and are way too dangerous to be around...but still, they insist on buying firearms and shooting them into the air on New Years eve.