I went to Olive Garden one year for my mom's birthday. The Olive Garden did provide a cake to my mom and we had a good time. When the bill came, we noticed they charged us a small fee for the cake.

On another birthday ocassion my mom was able to bring in a store bought cake to the restaurant.

Each restaurant is different, if a birthday cake meant a lot to you, you should have called the restaurant to see what they offered or could do for you to make the experience more enjoyable.