When my kids began getting close to the age of learning the handgun, I got a Ruger Super Single Six for training. Something that was a repeater, but where they had to do more "work" for each shot, over a semi auto.
Turned out to be a lot more useful than just something to teach the kids with, and of course, I still have and use it.
As they grew and moved on to centerfires, my son had a preference for the .45 auto, and my daughter, while not all that enthusiastic proved capable of doing some astounding good work with a .357 Highway Patrolman. (and much better than her "boyfriend" at the time,
)
just out of curiosity, why the 9mm over shooting .38 specials in your Matt Dillon Jr gun??
I handload, and bulk .38 SPL is one of the things I did, regular 158s at approx 850fps.