i have a coworker in that same physical issue, and older then the ops friend and my coworker loves her sks loaded down with any american made jsp....
a shotgun in 20 or 12 guage would be a waste of time. to much gun for not enough person. even if you factored in "reduced recoil" ammo, the lack of ability to work the gun cannot be over come. a double barrel .410 or 16 guage with real buck shot would be nice. even in a semi auto format. even youth model shotguns arent meant for someone under 5 foot.
a hi point carbine would be perfect.... in 9mm. even one of the old 9mm ruger police carbines in 9mm would be perfect.