Walmart gun? Did he mean it won't work? Or only work with a non-union shooter?
I don't think you would have any problems with the CD, they are known for their shotguns. But if you're looking to modify it, add bells and whistles, the Mossberg or Remington would be a better choice.
The only way to know if Laurie would have a problem with a 12-gauge would be to have her shoot one. Know anyone with a shotgun she could try? A 20-gauge should have not-so-bad felt recoil.
Just curious, have you shot a 12-guage with a pistol grip? I had a Mossberg 500 12-gauge that came with one. I put it on, went to the range, shot it, went home, and put the stock right back on. You wouldn't have any problem maneuvering in a residence with a stocked shotgun with an 18-inch barrel.