.22s are inexpensive guns and the ammo is cheap. If all you want to do is shoot at targets with your son, then that is the way to go.
If you are thinking about self-defense at all, then you probably want to go ahead and invest in a larger caliber. 9mm is probably the cheapest ammo, and so that caliber would make sense for target/defense.
You've read the old posts, so you know what most of us will advise: go to the range often and rent different guns. Rent them in different calibers, too.
You will find one that you shoot better or that feels better in your hand. That is the one you will want to buy. Enjoy the research part of this, it can be fun, and a great way to continue to bond with your son. You might even talk your wife into going out to the range to get her opinion about the guns you are interested in.
Know that there is going to be no "bad decision" here. Whatever gun you end up with will be great, will be fun.
Oh yeah, it will also only be your "first" gun, not just your only gun.
That is my opinion, but I'm not a guru. I'm sure you will get more words of wisdom from the really great folks on this forum.