Everyone is chiming in with good and accurate posts on this...way to go fellow MWTers!
The Kahr PM9 is considered by many to be "the" concealed carry gun. 6+1 capacity (7+1 with the extended mag) in a very small package. Can slip it in a DeSantis Nemisis pocket holster and it all but disappears.
I have had one of these for years. Haven't had *too* many issues with it. My biggest gripe with it is about chambering the first round. Sometimes, just racking the slide to load the first round doesn't fully return the slide to the firing position. You have to give the slide a good rap on the back to get it to return to the firing position. It is a known issue with these guns...even the manual says that to properly chamber the first round, lock the slide back and then using the slide release, let it slam the first round into the chamber...not a huge deal, but just an annoyance.
I just recently went through the agonizing process of choosing another CCW gun. Since I already had the Kahr, my decision process was prolly a little different than your Dad's. I looked at the Walther PPS9, another Kahr (CW9), and the Glock 26.
I about went with the Walther. I read too many folks having issues with their grips and mag release...so I stayed away from them. I was very tempted to go this route anyway. Talk to Rat...he recently picked up one in .40. Looks like a very fine gun!
Liking a thin gun for carry, I then started looking at the cheaper Kahr offerings...in particular, the CW9. Started reading up on it...and found some issues with the mag well swelling up and not feeding rounds properly. That DQed this one for me.
I'm about to contradict my "liking a thin gun for carry" line of thinking. I ended up with a Glock 26 (subcompact 9mm). The first pistol I ever had was a Glock, and have owned a couple over the years. Love 'em or hate 'em, they are some of the toughest and most reliable pistols ever produced. I am very confident that when I need that little pistol to go bang, it is going to. Plus it has a 10+1 capacity. I don't feel "undergunned" at all with this iron on my hip. It is noticeably thicker than the other guns mentioned here, but like I said, I already have a PM9, so I was looking for something to round out my carry choices. It is hard to go wrong with a Glock...
The S&W 642 (hammerless stainless .38 +p rated) is another great choice...I am still considering picking one up. There is a great one for sale on this site and I can't believe nobody has jumped on it yet.
Sorry for the long post...hope I provided some useful information for you and thought I'd share my recent experience/decision process. It comes down to what gun feels comfortable to him to carry and shoot.