Yes, MANY Guests ship all sorts of things to WDW and lots do come from amazon, ebay, etc. Having worked at a WDW resort that dealt with getting hundreds of packages on a daily basis I recommend the following to ensure that you get your package in a timely manner.
1. Ensure that whoever the package is being shipped "to" is a Guest listed on the reservation.
2. Ensure that the spelling of the Guests name is EXACTLY as it is listed on the reservation
3. Insert the word "Guest" into the shipping information with your name (ex. John Smith - Hotel Guest)
4. If it's possible, when entering the shipping information put your resort reservation number.
5. Ensure that you give yourself at least a 48hr buffer window between the date your package is set to arrive and the day that you leave. Items not picked up after a Guest has left will be returned to sender.
6. Don't send the package too early. Packages that are sent to the resort well before a check-in date will also likely be returned to sender (window of time and logistics on this vary from resort to resort).
7. Retain the tracking number (the actual tracking number...not the shipping ID, product number or anything else) and BRING IT WITH YOU TO THE RESORT.
8. When you check in, alert them that you are expecting a package. Give them the tracking number so it can be entered into your resort reservation information. (This helps those that manage the packages verify that it is indeed your package when it arrives at the resort).
9. Should your package say that it has arrived at the resort, it DOES NOT mean that it is ready to be given to you. It just means that it has arrived at the resort and is currently being sorted. Depending on what time of year you arrive and how many packages were delivered that day it can take up to 24-48hrs to process the package and have it delivered to you. Be patient. Should it be a time sensitive item, if you see it has been delivered to your resort you can call or stop by the front desk to see if it has been processed by the Disney package tracking system. Note that some resorts get so many packages that they don't have them in the main building of the hotel and use a separate nearby facility.
I know it's a lot of steps but should you do them all you should have a very good chance of getting your package in a timely manner. Hope that helps! Have a great trip!