If you're a mom, one of the most common complaints is that everybody will eat cereal up in no time. While that is a bummer (the stuff is not cheap, after all) at least you don't need to worry about rotating it!
I would recommend at least a couple of boxes per person. Yes, it's going to be expensive. But at least you know it's going to be eaten. Just bite the bullet and remember that the prophet commanded us to have a three-month supply of food we normally eat. So I guess that means the prophet wants us to buy cereal!