I think the first thing to do is enroll them in a basic firearm safety class, preferably one that let's them learn on .22 handguns. If they're afraid of guns, as you said, learning how to handle them safely from an objective instructor (i.e., not a family member) may help them get over this issue. Even just taking them to a shooting range to watch other people shoot may help.

As far as guns, based on what you've said, I think the DA revolver is a good choice. I agree with Mister X that DAO would be ideal (and I like the idea of the SP101 DAO), but a gun they have would be a good start. I think one of the best features of a DA revolver for HD is that they tend to handle neglect very well. They don't require the same level of regular maintenance that semi-autos need.

I think training is important, at the very least some basic safety/marksmanship training and education on self defense laws. While ongoing training and practice is a good thing, I don't think it's essential for self defense. There are plenty of accounts of people successfully defending themselves with minimal-to-no training, just as there are accounts of people unsuccessfully defending themselves who have had training. Does training and practice improve one's odds of surviving a deadly force encounter? Sure. But a lack of training doesn't automatically mean one is doomed to failure.