Thanks to both of you for your replies. I know gift giving has lots of implications in Japan, so I had to ask first.

Although this is obviously how they make their living, I don't consider this ryokan to be a "hotel." I think there are 4 rooms. It's more of a B&B.

I definitely won't add add a gift, but will consider a hand-made card. This is really going to be a special New Year's eve, much thanks to their help.

(if others have additional thoughts, I'd like to hear them.)