When I was a kid, we used to leave out on the counter MANY things that today "have to be" refrigerated. Pecan pie is one of those things. Admittedly, with five kids in the family, pies didn't last as long as they do at my house today, so spoilage wasn't much of an issue; however, I know we'd have multiple pies on the counter, and they sat out at least 2-3 days.
If you decide to mail the pie, I'd suggest that you plan carefully. Have your mailing items ready, bake the pie in the morning and get it sent out that same day. Let them know that it's on the way and let them know what day it was prepared.
Alternately, you could go "safe" and mail them the main ingredients -- pecans and all the dry ingredients mixed up in a bag -- along with your recipe. Kind of a pecan pie kit.