I tried and tried to talk to the post office about delivery but they were not very helpful. I worried myself sick. As it turned out, the girls arrived after only two days and they called me immediately. They will put your number on the box (at least MyPetChicken does.) The girls came to the post office I did NOT expect them to be delivered to which is why I couldn't get a straight answer from my questions during my visits.
As it turned out, I lost my little buff silkie on the second day, regardless of the timing and the weather. Touch and go with my little barred rock for awhile, but I think she is going to be okay. (Yayyyy Apple Cider Vinegar with the Mother, hard boiled eggs, and yogurt.) She's just pretty tiny, even as a bantam I think.
I know this waiting and worrying is hard. Let us know how they do. Happy Chicken Day to you!