My girlfriend has always wanted to be serenaded: Am I going to embarrass myself?

I'm planning to sing to my girlfriend on her birthday, and need to know if my voice will suffice. If it does, does anyone have any tips on how to improve it? I'm a musician, so I can hear intonation problems, but have no clue how to improve my tone or breathing. Any help would be greatly appreciated. This is me singing in an iPhone mic: http://www.youtube.com/watch?v=OgzRtCuN_xg

Edit: I'm a 16 year old male, no singing experience. [Critique] in title.