[BoogieMan]

To the OP: I am in a similar predicament with my daughter. She wants to shoot pretty bad. She is only 7 so I am insisting on the 22 for now.
Back to were you are. .410 is very tough to hit anything with. A 28 would be a much better choice. The downfall to both is the high cost of shells and the usefulness of the gun other than target. If I were you I would check into the 20LITE loads. It may allow him to shoot the gun for now, and with the 20 he can move up. Youth models from most manufacturers or just cut the stock down. As he grows you can always block the stock.
My first gun was a 870 Wingmaster youth in 20ga. I was about 10 or so and I shot that thing until I was about 15. I used it for my boys who have just recently outgrown it. My daughter will get it next as soon as she is up to the task.
If you need to lighten further consider a semi-auto 20ga.
Thats just my $0.02. I have never been a fan of .410's.