What’s the simplest reliable way to track attendance with barcode cards?

If you keep the current barcode system, use a standalone USB or Bluetooth scanner connected to a small computer or tablet and put a very small check-in program in front of the spreadsheet. The program should launch automatically, accept one scan, save the timestamp and member number, clear itself, and recover from an accidental click. The spreadsheet should only be used for reporting, not as the volunteer-facing interface.

Consider replacing the barcode cards with RFID or NFC cards and using a dedicated reader. Members would tap their card on a fixed reader, and the reader or a small computer could record the member ID and timestamp automatically. That avoids cameras, touch keyboards, browser focus problems, and keeping a camera stream running. It costs more up front, but it may be much easier for volunteers to operate.

A Google Form could provide a simple middle ground. Make the barcode value the only field, configure the form to submit immediately after each scan, and have the responses land in a sheet. Use a physical Bluetooth barcode scanner rather than the iPad camera; it behaves like a keyboard and is generally much more dependable for repeated scans. A kiosk-style tablet stand and a clearly labeled form shortcut would reduce accidental navigation.

A dedicated check-in product may be a better fit than trying to make Google Sheets act like an attendance terminal. Look for a visitor or community-center check-in system that supports barcode or QR-code membership cards, runs in kiosk mode, and exports attendance data to CSV or Google Sheets. The important features are automatic focus, one-scan submission, and a way to recover if the device loses connection.