Out of the ones listed, I'd agree with a guinea pig. Like all animals, they'll take work, but they seem less flighty and more willing to sit on a kid's lap. =]

I agree with what has already been mentioned. A pair of rats would be great! In most cases, they're much more calm than mice or hamsters, plus, most of mine just like to cuddle (as in snuggling up to my neck while I walk around the house or to snuggle into the pocket or sleeve of a hoodie).

Good luck!