This all day long. There's a reason there's not much to choose from.
Again have you actually used one or just think they sound good?
As Tony said the Buckmark series.
As I said the SR22.
Both superior in every way to the Heritage. Both meet all 3 of your wants.
Both are affordable.
Both are a better training tool for your kid.
If you insist on the revolver the Taurus as Tony said is a far better choice.
Chippawa makes one too, budget minded yet still better than the Heritage.
The problem I've found with teaching people anything, shooting and kids included, is nobody learns when there's not an interest or enjoyment.
You will lose both of those key aspects trying to teach anyone to shoot with the Heritage and likely any single action revolver.
They will shoot all day long with an SR22