Thirteen of us went in October and got there on a Friday. I sent our packages on Monday via UPS. UPS has a tracking system that can't be beat!
Some of the things we sent were:
diapers
wipes
tossable dishcloths (for the mugs we bought when we got there)
paper towels
disposable spoons, forks, knives and bowls
rain ponchos
cereal
fruit boxes
peanut butter in a sqeeze tube
snack crackers
raisins
graham crackers
fruit bars
breakfast bars
coffee (packed the pot in our luggage)
coffee creamer
hot chocolate mix
instant oatmeal
Water bottles - 1 each to be refilled at the parks each day, and bunches of the Crystal Light individual packettes to flavor the water.
Can't remember what else.... 52 pounds total!!
Sent them to myself care of Pop Century, with our arrival date and reservation number taped to the top and all sides of each box. Confirmed that they got there before we ever arrrived by tracking in online. Btw, one of the boxes was a lime-green stereo box, and that was very handy when it came time to have them sent to the room. Very identifiable!
HTH!!