I agree with most of the things that have already been mentioned here (except for the mango stuff - and when you two go to a restaurant, please make sure there isn't any HAGGIS on the menu), what really matters - no matter how gay this might sound - is that it comes from your heart. When this is the case, it doesn't matter how much effort/ time/ money/ whatever you put into getting or doing it. Hey, you are a musician, so writing a song for him is an obvious choice
Btw, Fragility - great timing. On Friday, me and my girlfriend had our first year anniversary. I wrote her something very personal, and considering the atmosphere, I think it was just the right thing. Although I couldn't invite her to a restaurant since her knees hurt really bad and she prefered staying at home, it was such a good day.