Hi there Dana,
You can certainly order items from the Disney Store and you can opt to have them shipped directly to Pop Century so they'll be waiting when you arrive. If you're interested in having a special surprise setup in the room and waiting for the guest of honor, your best bet will be
Disney Floral and Gifts.
The Dream Makers at Disney Floral and Gifts specialize in creating surprises whether simple or over the top. You can even have them orchestrate a complete
in-room celebration to take the surprise to a whole new level!
If you do decide to ship items ordered from the Disney Store, you will be able to retrieve your package at check-in, and hopefully you'll be able to have someone whisk the birthday girl away in time to set it all up for her!
The shipping address for Pop Century is as follows. I have created a sample label so you can see the type of info that is needed on the label!
Disney's Pop Century Resort
GUEST JANE DOE ~ Check In 12/15
1050 Century Drive
Lake Buena Vista, FL 32830
Hope this helps you plan a magical birthday celebration for your little princess!
-Amanda F.