My 2 cents: Skip the .410 and get a 28 gauge instead. It has all of the advantges of the .410 and none of the disadvantages. And you can get 1.0 ounce factory loads. For that matter, any kid 12 years old can shoot a 20 gauge with 7/8 ounce or more of shot.
Agreed. I would not let my sons shoot a shotgun until they could handle light 20 gauge loads. They are both excellent wing shooters. My oldest limited on his first dove hunt at age 12.