Hi Amy!
A six inch celebration cake can be added to your table service meal at any Disney-owned restaurant on site. You can subtly request one at the hostess desk when you arrive to check in for your reservation and provide instructions as to how & when you'd like to be presented to your guest at the table. The cost of the cake will be added to your check. This cake type serves about 4 guests and usually both chocolate & vanilla are on hand and available.
If you're unable to do arrange it "subtly" with your guest of honor in tow, make a bathroom exit from your table once seated and visit the hostess again then who can help the surprise & details to be coordinated with your server for you secretly! sssssshhhhhhhhhh ...
Should you prefer to
Customize Your Celebration with a specific cake flavor, type, size or other personalization, you can order in advance by calling Disney's Cake Ordering hotline at (407)827-2253. A minimum of 48 hours notice is required.
Be sure to visit Guest Services in the park to receive a 'Happy Birthday' button so that Cast Members all around the park can acknowledge your Birthday Guest all day long!
Pricing for a 2-Day Walt Disney World Park ticket is the same online (using Will Call pick up) as it is at the ticket booth kiosks at a park gate. It's a matter of convenience & time really - whether you choose to purchase in advance or don't mind waiting in line on the day you arrive before jumping right into the fun!
Wishing you a Magical time celebrating a Birthday at Walt Disney World!
Kirsten