I started with holidays about a year into my fade. I still do not go crazy because of my family. Anyway, just ease into it, and take your time. Actually, there are a lot of holiday things JW people do that they excuse away such as enjoying Christmas lights, eating Halloween candy, and wishing one another a happy birthday (or a congratulations).
While she may object to holiday decor in your home, like a Christmas tree, she likely will not object to it at a high-class resort or comfortable inn. Perhaps take her out to celebrate the holidays and surprise her with a gift. Don't forget her birthday either. It will make her feel special and loved. A lot of JWs I know actually enjoy having an unbelieving mate because they get the best of both worlds.