Where do you live? I might see you at the local Costco !! Make sure they are open on Presidents Day (the Costco near me is often closed on Memorial Day and 4th of July). Also make sure that Kelloggs would accept the order forms with a pre-made label (use an old address sticker label) if you decide to go that way.
Last year, I did a similar promo, not quite as lucrative, but got Delta points for buying Diet Coke products at my local supermarket. Needed 6,700 points for 25,000 Delta miles. Each 2 liter bottle of Diet Coke was 50 points. There were some multiple purchase bonuses. Anyway, the total cost for my 25,000 Delta points was around $180, plus I got all that soda. Cashiers let me sneak through some Cokes, Sprite and Orange so I wouldn't be stuck with all Diet. Did end up donating lots to the local schools every time they had a Bingo Night or fundraiser. But you should have seen the piles of soda in my basement !!!
GOOD LUCK !!!