i've shipped boxes several times to save room in the suitcases (and to hide a few small toys for the kids to play with while we collapes after the flight).
i just checked the toys r us website (
www.toysrus.com)-you can order diapers, wipes, some types of powdered formulas and just about anything else you might need. they are currently running a promotion where certian purchases over $25 (us dollars) qualifies you for free shipping and handleing-but they run this special on a very regular basis. as for cereals and snacks, you could pack a small supply and then grab some on site at one of the many "general stores" If i recall they carried jarred baby food as well)-if you are staying at a disney vacation club resort you can even make a grocery order from thier list which they will put in you fridge prior to your arrival.
just contact the resort you're staying at, clear that it's o.k. and ask the earliest date they would accept a package to hold for your arrival, then figure out how long the shipping will take from your provider and come up with an order date. find out how the resort wants you to address the package (most want your name, est. date of arrival, reservation number...).
and don't stress out-all of the parks at wdw have baby stations where you can get jarred food, diapers, wipes and minor snacks at a price (they also are an oasis of quiet for changing or feeding a little one).
in closeing-if you want to email me with a general idea of what you're looking for (and what price you normaly pay (in us $ please)). i would be more than happy to surf the net and email you some reputable sites that you can access for some more info.
barkley mom
one thing i feel i must caution you on-i recently watched an episode of airport and learned that liquid formula (with the exception of a reasonable amount to cover the flight time) may be denied as acceptable luggage. apparantly it has something to do with what formulas are acceptable by what country's standards. so don't plan on packing enough cans and then have them confiscated before take off.