The bonus cards for $5 can only be used before July 31. The $25 gift cards don't expire.
You must order buy the gift card by June 30 to get the $5 bonus card. No limit on how many sets you can buy. But, only one bonus card per visit.
So, if you order 3 gift cards ($75) you get three bonus cards ($15). If you got out to dinner and the bill comes to $100 you can use all three gift cards but only one of the $5 bonus cards.