I agree with setting their status to "Inactive". In order to zero out the balance due on their Fees representing the annual dues, you could waive the balance due. To do this, open the family's Household Ledger and on the Fees grid, right-click the specific record you want to waive, and from the popup menu select "Waive Fee". You can also select and waive Fee balances from the main Ledger > Fees grid.