Hi there!
We stayed at the Poly for our 5th Wedding Anniversary in May.
Prior to our arrival I called the GF bakery and ordered two of the small castle cakes.
For pics go to (just put www in front):
weluvdisney.smugmug.com/gallery/1499890/27/71912860
Approximate cost was $12 per cake.
We picked up the cakes near the front desk at the GF. The GF bakery asked us when we would be flying n and approx time we would be picking up the cakes. GF bakery asked us to go to the GF front desk when we arrived and then ask one of the CM to call the bakery. We did just that. Then one of the bakery cm met us in the GF lobby with the cakes.
GF bakery will not deliver to other resorts on property, but you can pick up the cake(s) your self.
I'll go see if I can dig up the number for the GF bakery.