I think these promotions are a great way to get customers into their stores. This one even adds a charitable component which is certainly a plus.
However, for the consumer, is it really worth the time? Depending on how well publicized this is, the crowds could be significant. I remember seeing long lines at Denny's for their free promo but I think they gave away a full breakfast. This is just for 3 small pancakes.
Considering the trade off between time and money, how long is it reasonable to wait in line for this? I don't go to IHOP anymore (since I discovered the Original Pancake House), so I don't know what a Short Stack costs. I can't imagine it's more than $4.