Hi Kristina,
You're welcome to mail packages to yourself at your resort. You can do this via the DisneyStore.com website or you can box things up and mail them to yourself using USPS, UPS, FedEx, etc.
The mailing address of Coronado Springs is: Disney's Coronado Springs Resort, 1000 W Buena Vista Dr, Lake Buena Vista, FL 32830. You should put your name, your arrival date, and the word GUEST on the package.
While you can send yourself packages, they cannot be delivered directly to your room or set up in your room prior to your arrival. Even the Disney Florist does not place items in guest rooms in advance. Final room assignment does not happen until the guest actually checks in.
My suggestion would be mail yourself some boxes and then send your family off on an errand. You can set things up yourself and no one will be the wiser.
Please let us know if you have additional questions. We're happy to help.