Little boy got Charlie when he was 6 and couldn't really hold him without careful supervision. He was careful and knew that Charlie could be injured and he had to be gentle, so he had the right attitude but didn't know his own strength sometimes
Plus he tended to try and hold onto Charlie out of panic he might run away and squeezed a bit then. He also got in the bath with him during taming and enjoyed that. He is 8 now and better at holding him, but still has his moments where he forgets the hamster is not a toy.
So I'd say - constant supervision with a child up to about 10 years old maybe. Girls may be gentler though!