Here's another vote for the Beretta with tip-up barrel. Not a big fan of .380, but beats a stern look of disapproval, and it requires less hand strength than other pistols.
Another option is to build a "cocking jig." (Insert Beavis/Butthead joke here.) A pistol's slide can be operated by pushing it against a table edge, but that is precarious -- the front of the slide can slip off the table edge. Good thing to know for emergencies, but not for regular administrative handling.
You can build a device with a hole through the center, and a very short cylinder/pipe to guide the pistol, so it does not slip out of position. Push against the pistol and the barrel goes through the hole while the slide retracts. Brace it sturdily, on a heavy desk or workbench, pointed at a bulletproof backstop, and you can use it as a slide operator.
i just tried something like that with my beretta 92fs. if i rest the front of the rear site against the top of my belt, i can easily rack the slide by just pressing down. it requires on hand and minimal effort
Okay folks, here's an update. Got to go home this past weekend and went to a shooting expo with my dad where he got to try out some guns. He LOVES the .45 1911 (and has no real problem racking the slide of a broken in pistol). Aparently, I was talking up the recoil of it before he shot it to "prep" him for some pain. He shot and said "oh, that's not bad at all!" Great fun! Anyway, he's pretty sold on the .45 1911, specifically Smith & Wesson (and I have to admit, that is a very nice 1911). Anyway, just food for thought.
I've read that S&W will soon reissue their "Centennial" .38 Special revolver with a grip safety (resurrecting the old "lemon squeezer"). Since an external safety is a concern of your dad's, that may be an option. If, of course, it really happens. Supposedly, one of the variations will have a color case-hardened frame, adding to the nostalgia without detracting from its functionality.
I recently purchased a sig x-five allround in 9mm. Recoil is almost nonexistent, the slide is easy and it's DA/SA.
BTW, very easy to disassemble and reassemble. Much less finicky than my 1911.
Same advice for motorcycles, wives and guns. He should get the one(s) he likes the best!