I would guess that would be up to him (oh..i mean you

). We were there last December for our honeymoon. We had been married actually 3 months prior, but that is what we were celebrating. So I wore the pin the whole week.
I don't think you will get in "trouble" for wearing it all week. When we were wearing them all that really happened was a bunch of people told us congratulations! Even characters! We didn't get anything extra (not that we were expecting it). Just know that you won't be getting extra goodies maybe now thought with the yoamd), so you won't feel bad if he wears it on days other than is actually birthday.
Have fun and Happy Birthday!