Export the adult child's record from this copy of the family record. It will default to a new family record in which the adult child is a registered, active, head-of-household member.
All of the sacramental records will follow the member to the new church
The original church will retain a copy of this member's records with the following attributes:
This person will no longer be in the original family record but will be the head-of-household in their own family record
The record will show the member as inactive and non-registered
All of the religious education records and giving records stay with the first church
The original record in the former church will continue to keep all of the contribution records for this person. This cannot be transferred for several reasons: 1) these are records of contributions to the former church and 2) the new church does not have the same funds, etc.