agree w/ others, 410 is a bit much for age 6
for most, age 9-10 is about right
learning to hunt w/ Dad is great, just "being there" w/ Dad is great, but not the best way to teach them to shoot. Better done methinks, with a right sized 22 at the range, real close attention and total focus on the child, not adults shooting.
but obliged to respectfully disagree w/ those who say 410 not enough gun to 1st learn with, re: they will "miss too much".
Not true for us, always started ours with a 410. The "trick" is, presuming child of age and temperament to be ready, a gun which fits them well, and shoulders naturally (same as for any adult).
I was real lucky a few decades ago, to find a "matched pair" of nicely made single shots truly built to "kid size" and "little lady size" not chopped down, but built right size. Not pricey guns, either, just built right sized, a bit unusual. Start 'em with light clay loads, don't tell them they are expected to miss, don't overdo the instruction, just let them shoot, safety supervised. They will miss the first 10 or so, virtually certain, but once they find their own swing, get a hit or two, it can be pretty stunning how quickly their hit ratio picks up.
may have something to do with learning that a close miss is not a hit, only a hit is a hit, I dunno, but they figure out pretty quickly what being on target is, if you are patient and do not burden them with too much daddy expertise.
Nothing beats that "instant feedback" factor in any learning process, not even expert training.
then again, most people say "not so".. and there are a lot more of them then there are of me, so....
PS
if he has a suitable 22 single shot right sized, and you are choosing his shots for him (assumed) from a appropriate position with safe backdrop
put a red dot on it for him... hard to tell if li'l guys are really looking at 'sight picture' you think they are, red dot makes it unmistakable