you can get an HR in 28 also, a bit more shot in the pattern than a 410.
I started with a 410 too,couldn't hit squat with it,moved up to 20 ga and started having success.both of my nephews started with a 28 and are pretty good shot's with it.
Unless he is very young or small, I would check around for a used youth 20 o/u or SxS. The Stoger Condor Youth is great, about $350 + paperwork. They get used to the safety and trigger(s) quicker than you think. You can also restock an adult size gun to fit him (nothing fancy). In my opinion kids grow out of "little .410's" too quick, the're ill-fitting and the hammers are a handicap. You can get Little skeeters gauge reducers and use .410 or 28 gauge shells in the gun to start him and get much more use, and probably better results with the gun. Ya' get what ya' pay for.
I bought my son a Rossi starter .410/.22 combo at Dicks for $100. The .22 is great, but the .410 kicks like a mule because of it's lightweight. Hell it left a bruise on my arm! Mine weighs 3 pounds.
The one Ken is showing is 7.4 pounds and that 4 pounds of weight makes all the difference. My point being, don't get a "light" gun because it's for a kid. One gets used to the weight, but not the kick. Just my advice.[up]
I'm on a major 410 kick right now. In the last 3 months I bought a 311e & a 311a dcs 410s. Both in great shape & both under 200. Add them to the 2 410 single shots in the closet & I cam start an army with 5 yearolds.
Ppl on this site gave you great advice... go with a 20.