Call the number for the Contemporary and ask to be transferred to Private Dining. Then explain the issue to the that CM and have them write down your entire order. There is no standard mini cake, so if you want a specific style, be sure to send images to that email and have the CM write down that you sent images. Then call Private Dining back 2 or 3 days before you get there to reconfirm everything. Prices for mini cakes are listed in Post #2 under each resort/park's entry. Mini cakes start at around $35, but the price depends on how elaborate you want the decorations.