So, my wife and stepkids completed the NRA Basic Pistol course just over a month ago, and all three did pretty well with it. Somewhat surprisingly, all three expressed a fair amount of interest in continued practice. David's not going to have any problems using my 1911 - he's nearly as tall as I am, and his hands are just a touch smaller than mine, so he can comfortably hold the .45. My wife Lori and stepdaughter Alison both have considerably smaller and weaker hands than David or myself, and have said that they'd prefer something smaller and lighter than the 1911 for regular practice.
Lori has come to the conclusion that she'd prefer a revolver for "her gun", as she believes it will be easier to operate than the semi-auto 1911. I'm leaning towards a moderate or light .38+P/.357Mag revolver (loaded with .38Spl for practice and probably .38+P for defense), but have always preferred semiautos myself so I don't have a good feel for what might be a good choice to start looking at. She's 5'5" and not terribly strong, with small hands, and has difficulty properly manipulating the controls on my 1911. She had trouble with the slide, for example, and thinks the 1911 is too heavy for her to use outside of emergency.
Alison is highly unlikely to have to use either my 1911 or Lori's revolver, although she'll likely do at least a little practice with Lori's revolver once we get it, against the possibility that she'll need to use it. She's about 5'6", a little stronger than her mom thanks to better exercise habits but very slender and with very small hands - she also had trouble manipulating the 1911's slide, come to think of it. For her range use (and probably to be used by the rest of us as well), I'm thinking a .22LR of some kind, either revolver or semi-auto. Probably leaning towards revolver, actually, as David can use my Colt and can practice with that (or with a .22LR upper on the Colt frame), so something Lori and Alison can use to practice that's similar in function to the larger-caliber defensive revolver would likely be good.
There's no real rush on this - it will be some time before I can afford to buy one additional pistol, let alone two, and I'll need another pistol safe - but starting to get info early can't do anything but help. I'd obviously prefer to keep price down to the extent possible, without dipping into Lorcin territory, say.