Regardless of the make and model,,,
You need to decide between a Target style or one resembling a duty style pistol.
Target styles are the Ruger Mk and 22/45 series, the Beretta NEOS, S&W 22A, and the Browning Buckmark.
I own all five of these and they are all very nice guns.
Duty style pistols are like the S&W M&P, the M&P Compact, Sig Mosquito, Ruger SR-22, Bersa Thunder 22, etc.
Target styles are all single action with no exposed hammer,,,
They are great for hunting, target shooting, and all around sport shooting.
Duty style pistols can be of different actions.
For example the S&W M&P Compact,,,
Is what is called Hammerless Single-Action.
When you work the action to chamber a round,,,
That action also cocks the internal hammer,,,
There is no way to de-cock the hammer,,,
You rely solely on the manual safety.
The Ruger SR-22 is a SA/DA with exposed hammer and de-cocker,,,
Working the action to chamber a round cocks the hammer,,,
You may de-cock the pistol with the de-cocker,,,
Or as in the S&W M&P Compact,,,
Rely on the manual safety.
Any style of these pistols will do your son very nicely.
Target styles are probably better for paper punching games,,,
The duty styles will be better for self defense training.
My preference is for a SA/DA with exposed hammer and de-cocker,,,
But there is absolutely nothing wrong with the other types.
JMHO
Aarond
.