My ducks had no problem shipping, but this is my first time, and they weren't call ducks... =X
I ordered from McMurray, and only one of my Cayugas was even remotely 'worse off' than the rest. Her only problem was her eyes were kind of crusted over for a couple days, and I had to wash them off a lot. As a precaution, I gave her some sugar water a couple times, but I think Gatorade or something would have been better; it's got electrolytes (however you spell it).
Make sure you check them at the Post Office, so any staff there can be witnesses in case one of them is DOA.
Also, you know not to let them in a pool on their own for a little while eh?
(I'm BAAAAAD... =P I let them have a supervised swim, dried them off, and then made sure they were warm a couple times a day.) BUT, don't let them doodle around in their water dishes and get cold and wet either...