RE: revolver calibers
If you don't handload, seriously consider the .44 Magnum with a good set of grips. I really like the Ruger Redhawk and Super Redhawk. Strong, accurate guns that are reasonably priced.
If you handload then my suggestion would be to go with a Ruger Super Redhawk in .454 Casull, once again with good grips. Now, the .454 Casull is, to be perfectly honest, quite a handful especially with heavy bullets. But the beauty of the .454 Casull is that you can use .45 Colt without any loss of accuracy, but still step up to full power .454 Casull loads when you're ready and the need arises. And if you handload you can take advantage of the strength of the SRH and load .45 Colt to +P+ pressures (safely with published and tested load data, see Hornady Handbook) and easily duplicate .44 Mag performance. Then when you just want to plink you can use mild cowboy action ammo and it'll feel like shooting a 9mm.
Oh, and one last thing. When you or your dad start shooting powerful handguns like these, I strongly suggest you invest in a good shooting glove with a padded palm and web area, and a very good pair of ear-muff style hearing protectors (and ear plugs too is even better). This will make your practice experience MUCH more pleasant and productive with much less chance of developing a nasty flinch.
Mike