We asked for him to deliver the cake at bell services at AKL (Jambo). Once we arrived we picked it up (AKL bell services is always quick) and then informed the restaurant we had a cake with us while checking in. They told us they can’t take it back to the kitchen due to safety reasons and we had to keep it at our table. They provided candles and lit them up. They also do not provide any to go boxes, but it was easy enough to package it back up into the box. We chose not to cut it, but it would probably be better to cut it at a restaurant if it has fondant (vs trying with plastic knives). I suppose someone can step away and go to bell services if you would like it to be a surprise. I would make it the last thing you do so you can take it back to your resort after dinner.
We thought of taking it to our MK lunch ADR at CRT. He said he can deliver to the front of the park and meet up with us, but we would have to take it through security. Also someone would have to leave the park to take it back to the resort. The cake will go bad in about 1-2 hours in the Florida heat.
The cake was big for a 6 inch, most likely you will have left overs esp if you have young kids and you’re at a buffet.