We had the exact same idea. . racking up TONS of miles which is nice. However, it is still an additional $375 per person to upgrade our fligths to first class. AND, from what I read from their website, it is only a total of 3 free carryons (up to 70lbs) per person. . . For a two hour flight for us, seemed much more economical to give $40 cash to members of our bridal party to take an extra bag each . . . PLUS you must consider the $300 max value per person Mexican customs allows. BUT, we will use our United Club Passes the day we leave.. Arrive at the airport early and relax with bloody marys!