For someone not familiar with hand guns I would recommend a 22lr or 22mag3-4inch barrel 8/9 shot if possible. Then take him out often to shoot. I'm just not a big fan of 38sp stub for older folks. I seen a recent story of a senior in Kentucky I believe who stopped a home invasion with a ruger 10/22, light weight, short, 10 rounds.
I like the idea of any person having the ability to protect themselves sadly 911 usually arrives after the fact.