We shipped a box about 2 years ago to OKW and it worked out great. We were there for a week and traveling w/DS2 (at the time) plus his carseat, so we wanted to carry as little weight as possible in our suitcases. We shipped diapers, juice, glow bracelets and goofy little toys, larger bottles of shampoo, sunscreen, etc, wipes (Lysol and antibacterial hand wipes), snacks, umbrellas, ponchos, misting fans, and a few other heavier items.
I had called the front desk at OKW to find out exactly how to label the box, and I labeled 2 sides, the top, and put a paper inside with our info (I also bagged everything that might spill in ziplocs and then put everything into a garbage bag, just in case it sat on the tarmac in the rain or someone else's luggage leaked). I also included clear packing tape, scissors and a thick black permanent marker to repack the box and ship it home at the end of our vacation. I sent the huge box UPS about a week ahead of time. I called to make sure it had arrived a couple of days before our vacation (giving me time to pack another suitcase if the box was lost). It worked out really well, and at the end of our vacation we just repacked the box with dirty laundry and souvies, relabeled it and took it to the front desk to have them ship it back to our house.