Try buying the Pop Tart Pastry Swirls at Sam's (or Costco ?) for $4.96 for the pack with 300 miles. I do not know if they are 3 separate 100 miles certificates.
Also, in all my years of very extensive coupon use, I've never known a coupon to not scan because of expiration date- I don't think the date is even encoded in the upc of the coupon. If you trim the expiration date off, the expired coupons won't look expired.
Don't do that, though.
Since the supermarkets have 60 to 90 days after the expiration date to send the coupons in, they should not worry too much about expiration dates.
Richn