Switch family organizer
How can I switch the family organizer on family sharing?
Question marked as
Apple's support document Leave Family Sharing describes the process of leaving a family group. It does not mention "switching" from one organiser to another. Therefore it would seem that you would need to disband your current family group and have another (adult) organiser set up another family group and invite participants to that new group.
They also mention in the set up page that "...you can only switch to a different family group once per year.."