My cousin has 3 boys that have college paid for (he is a doctor) but he wishes to wash the payments through a credit card each month that gives him cash-back, or hotel or airline miles. What is the BEST DEAL out there?

I have an American Airlines Mastercard which gives me an AA mile for every dollar I spend. Discovercard also gives 1% cash back for every purchase, but usually, in August or September, they will give 5% back for purchases spent on education.