Id start with the rewards your dad already uses and ignore the rest for a month. My uncle tried tracking every offer, then got annoyed when grocery shopping took twice as long. Now he keeps gift cards beside his reusable bags and checks cashback when he gets home. Once, he wrote upside customer support in his errands notebook after noticing a question about one trip; it sat alongside reminders to buy milk and call his sister. A simple routine was easier for him to keep than a spreadsheet.