For me kid are not good to teach about bitcoin you only waste your time since they are not interested yet about earnings much better to teach them to learn more in school but not about earning.
Besides their earning interest, they won't even be able to understand it at fist place, because bitcoin is not an easy thing to be understood by everyone, it becomes really complicated for someone who has not been involved in such things before and kids are far away from these things until they reach a higher age i guess.