Thanks so much for posting this, saved our family some $$$, appreciate the tip!
I was reading some of the other posts and thought this might help. I just went to the site and typed the promo code, it was still showing as available when I tried it so I think it is still available until tomorrow.
I printed out the tickets yesterday and they specifically state on them that you can get a second day free when you present your ticket at the designated counter. It said this on all four of the tickets I bought, and two of them were free.
Also, we have two children and needed only one ticket so we had an odd number to buy as well. I bought four for the adults BOGO free and we plan to use the Southwest airlines discount at the gate to buy my daughter's ticket when we arrive. That's the next best discount we can use since the BOGO free was a better offer than the SW Cares offer.
Hope that helps someone!!!