Just a precaution. We shipped some stuff to CSR once through the US mail and the package got "lost" in the WDW's main mail room and the box was also nearly completely destroyed with several items missing because they fell out of huge holes in the box! It also took multiple phone calls and a lot of time trying to figure out what happened to the box and waiting in the room for it to be delivered, over and over again.
What I have read on the boards is to not ship through US Mail, but to use UPS or FedEx as they deliver directly to the resorts and bypass the general mail sorting area.
I'm going to suck it up and give it a try again this year, by shipping bottled water directly to the resort through UPS. I'm not counting on it getting there, so my expectations are quite low. That way, if it does get there, I'll be very happy!