Personally I think the necessity of concealed carry in a diaper warrants a stainless steel revolver. Perhaps a Smith and Wesson Model 60 Chief's Special with a 3" barrel loaded with the 'FBI load' 158 grain semi-wadcutter in .357 magnum. A good gunsmith can lighten the trigger pull in double action, although a well-trained toddler with strong thumbs may prefer single action.