In no particular order:

1) Ruger Single Six
2) Ruger Bearcat
3) S&W 4" M-34

2 of my granddaughters shoot my M-34 and Bearcat, ages 10 and 12. I think they like the Bearcat more, but that could be because they like the name

Of course, you could buy a Diamondback or 5 screw M-17, or pre, and put some outrageously oversized rubber grips on it. If your son doesn't like it, you might

I own the 3 listed above. He'll never feel he's outgrown the Single Six. JMHO...