As a 'wife' myself, I think your wife would appreciate your 'gift' no matter if it happens to be a piece she does not think is very romantic. On the other hand, you don't want to make her sad on her birthday. Sorry, but you have a pretty good dilema going here...
I'm not sure how well you can sightread or how quickly you can learn a piece, but if you want to try a different nocture, one that is not overly difficult and is romantic in nature, then I would suggest Op. 15/2, Op. 27/2 (my favorite!), Op. 32/1 - pretty easy except it ends on a minor chord which all of a sudden changes the whole feel of the piece. But you can play it as a major chord which is what I have done because it was marked that way in my book. There is also Op. 37/1 which is pretty easy. Best wishes!
