Obviously the laws in the USA are very different from our own, but I don't consider any pistol suitable for shooting pests apart from dispatching cage caught pests
I would advise you get some clarification on the details of the situation especially the shooting range & layout,

I'm guessing that his rifle is pretty high power hence it's hard to cock it, where a lower power rifle would require less cocking effort & might be an option for his wife,
another option is CO2 if it's legal over there, but whatever the choice it needs a shoulder stock so it can be aimed correctly.