Possibilities:
United as an airline to concentrate on. Between UA Explorer/Sapphire Preferred/Ink you and your wife could each get 3 bonuses, possibly every couple of years, plus miles from spending.
If you have lots of free cash, BankDirect can return LOTS of American miles very quickly.
Hilton for hotels. You and your wife could each potentially get 6 or 8 Citi Hilton cards (2 every 3-4 months) at 50K per card, with low minimum spend. Granted Hilton points are becoming like Skypesos but 300-400K per year times 2 of you times 5 years is a lot of pesos.
And of course, MS to increase whichever you choose.