Give the canteen runner a login that only opens the register — not your full Campistry account. Set a shared PIN below, then tell them to go to snacks.campistry.org and sign in with your Campistry email plus the PIN (standing in for a password). The PIN is a completely separate secret from your real password — it can never open your actual Campistry account, only the register. 5 wrong attempts in a row locks the register — it stays locked until you unlock it here, no time-based auto-unlock.

Which methods the office can record against a deposit. Debit cards are deliberately not offered — a canteen deposit is a prepaid balance a camper can later draw back out as cash, and card networks treat funding a cash-withdrawable balance from a debit card as a cash-equivalent transaction. Credit cards are fine.