There is also a school of thought that says the .410 isn't much of a kids' gun in that the smaller pattern makes it hard to learn with. In other words, the rewards of solid hits are harder to come by and kids lose interest or get discouraged.
I see the merits of that argument, but having learned to shoot with an H&R .410 myself (probably identical to the one you are thinking of butchering), I can't subcribe fully to it.
But, as Brent said, ammo don't cost what it used to and kids seem to get less time with their mentors in the outdoors these days, sadly.
I must also admit, Jack, that asking us to help you build a tackycool gun that will not be for actual use, cuts across the grain of many of the folks that browse the shotgun forum here. If you ask about heatsheilds, pistol grips, breacher barrels and whatnot, we typically will say, "don't".......