We have had bad luck with hermit crabs and small turtles. Aquariums (which is pretty much the type of environment both of them need, although the hermit crabs live in one filled with sand and shells, need certain things. Turtles have to have water that is constantly kept filtered and clean. The hermit crabs need a heated rock. Gradually, they all died. I do know people who have raised the red striped turtles successfully, but again, with well cared-for aquariums. And, if they are successful they can grow pretty large.
Our children, and our grandchildren, have always had cats. The great thing about cats is, if you have an indoor-outdoor cat, it will pretty much take csre of itself, as long as you have a dish with food and water, and a litter box somewhere inside like in a garage. If you get a kitten, although the tiniest ones are cutest, insist on it staying with its mother for at least 8 weeks. Older kittens and young cats can be quite fun, because they will chase after little balls, play with yarn and string, etc, but if they haven't been taken too young and therefore are neurotic, they can also be very loving pets who purr and will sit on your lap and even give you "kisses." Over 65 years of cat ownership, cats have been great pets, with few complications, and we have had many who lived to be quite old, although you need to bring them in at night if you have coyotes around.
We also have a bunny right now, and they can be litter box trained as well. They are messier than cats, however, can't go outside on their own, of course, and you need to clean out their litter more often and give them a bigger variety of foods. Also, of course, they're not going to chase after a ball. However, if you find one with the right temperament, they can be cuddly as well. Again, be sure they are large enough to leave their mother.
After reading other answers, I remember one real chore for one of the critters we had was constantly having to go to the pet store to buy some live insects for it -- crickets, I think. Even though there is some expense to getting a cat neutered, I'll take one any day, and children do love them. And I do suggest getting one from a shelter or a rescue place.