Egwina: *cooked* regular potatoes are fine! Just don't feed them raw, and especially not raw peels from regular potatoes.
That being said, I wouldn't feed raw sweet potatoes either.
BTW- don't eat potatoes yourself that have gone green-skinned (exposure to light makes them green), either, even cooked- unless you cut 1/8 down into the potato below the green peel. That's toxic for everyone... Solanine... anyway.
About cooked SWEET potatoes, they're great. Full o'beta carotene and vitamins you know. My girls looooove them. I regularly bake sweet potatoes for my family and make a couple extras, just plain bake them. The next day, the leftovers go out to my Ladies. I split them open and put it down, they bury their little beaks in there, all the way to the nostrils- can't get it down fast enough. Feathery piranhas.
Judith & Crew
7 hens 2 dogs 2 kids + 1 Chook-lovin' DH
Somewhere @ Columbus OH
Under Cover in Suburbia