On our 3 month holiday last year, we had Mrs NM's parents along with us. All the major bills (hotels, car rental, Eurail Passes, meals, sight seeing etc) were paid on my Amex at 1.5 points/A$. Then the inlaws just BPayed their portion of the costs into my Amex account. They don't even have a credit card! I had to set them up with a Visa Debit Card before we left so they would have something that could be used when I was not around with my Amex.