The softest kicking low recoil loads I have tried lately are Fiocchi's offering. Unfortunately I am not having much luck finding any more of it to buy right now, hope you can do better if you decide to try it. The stock number for the load I like is 12LE00BK.
Hornady TAP in the blue hulls might be a contender too, I haven't tried it yet myself but have heard some good things about it. The red- hulled loads designed to run semiautos are pretty manageable in pumpguns, and the patterns are great.
The Federal low-recoil offerings use the same wad that produces such great patterns in the Hornady loads. It's pretty widely available also, but I haven't yet tried any of it and can't comment on its recoil as compared to other reduced recoil offerings.
Remington's 'managed recoil' loads are pretty widely available and not too bad on the recoil scale by comparison. It's an 8-pellet 00 load at an advertised 1200FPS, and patterns reasonably well for me in several different guns I've tried it through. Stock number for it is RL12BK00, I got the stock I'm patterning with right now at wallyworld for less than $3 per box of 5 rounds.
There's no reason a healthy person can't handle a 12 gauge pump gun, many repeating 12s actually kick less with reduced recoil loads than lighter weight 20s in the same make/model do with full house buckshot. A critical element in felt recoil is gun fit to the shooter, another is good technique. Premium recoil pads (Remington R3, LimbSaver etc) can also make a difference. I don't know the person or the circumstances, but please don't be too hasty in putting down their choce of the larger bored gun. It may actually be a better idea than running magnum loads through a lighter weight 20 gauge gun.
Good luck helping your friend,
lpl/nc