Personally,I don't understand why you were invited to the wedding at all! I am always amazed when someone gets an invitation and you don't even know the bride or groom. If you are good friends with the parents and see them SEVERAL times a year, it is a bit more understandable but as your post indicated, your husband sees her father once a year.
I simply don't understand this. I think it is all about asking for gifts at that point, which I find incredibly tacky.
We recently received a wedding invitation for the daughter of an acquaintance of ours and do know the daughter but haven't seen or heard from her in at least five years, except for once at a soccer game. Her wedding is 6 hours away from our home and we have no intention of going. I also do not have any intention of sending a gift. We would, however, attend their other daughter's wedding and send a gift as my husband coached that daughter and she is a friend of our daughters.
I always think that when wedding invites show up and we haven't seen or heard from that person in a long time (or don't really know them) that the bride/groom are being greedy. Am I off base here?