"One dollar from every Big Mac sold will be donated to Ronald McDonald House"
Now, don't get me wrong, I'm sure Ronald McDonald House does some wonderful things for people. However, I'm pretty certain that the profit margin on a Big Mac is such that the profit per burger is more than $1. And, I'm sure you are aware that, despite recent difficulties, McDonalds is a massive, multinational, multi-billion dollar organisation.
So, how about this for McHappy Day? One whole day's takings is donated to charity.
Otherwise (and call me cynical if you like) it just seems like a cheap stunt to get people into the store so that you can sell, not only a crapload of Big Macs, but fries, Cokes and everything else that goes with them.