Nice cake. the people look almost superimposed on the background though. did you guassian blur the background seperately? I say that because the level of blur seems constant the further into the background you go. If you did do that, a good way to make it look a bit more convincing is to do it on a seperate layer and mask bits out at differing opacities so the effect gets stronger as you go deeper into the field.
Of course, i might be wasting my breath telling you this, but hey.
Fun cake. Not such a good photo. He seems to be posing for the shot, so you should have had the opportunity to compose it better. What's the point; is the girl part of the birthday present? Why is the second man in the photo? I think it would have been much more effective with just the two people, and with the girl out from behind the mans elbow.