I started CDing after around 35 years of marriage when my wife had to be away from home for an extended time. No real reason why it happened but I found I just loved it and dressing seem to fill a void which I had been unaware of. Told my wife a week after she came home as I can't keep something like that secret especially when you love someone & have shared so long together.
At first she has what seem to be the normal concerns about being gay, wanting to be a woman etc but I had found some resources on the net which I directed her to. We talked a lot and she accepted this was a new part of me. She is accepting and to some degree supportive. I dress around here and she will often say on the weekend "are you dressing tonight" or "why aren't you dressing tonight".
We have done a bit of shopping together and she has brought me a few things. Our sizing is similar and she lets me have a fairly free go at her closet. If she is cleaning clothes out I get first go at anything I want to keep. She wears some of my stuff.
I believe she supports me because I'm still the same person she has loved all those years. Our relationship has never been based on me doing all the "male" stuff and her doing the "female" stuff. I had all the domestic skills etc before we met and I probably taught her a lot of "female" stuff. My wife is a keen dressmaker and since the CDing I get consulted a lot more on fabric, styles etc as she has come to appreciate that I have an interest in things feminine.
I think CDing has added a dimension to our relationship which was not there before. My wife is very comfortable with who she is and I think that is a factor in acceptance. I can't see us ever going out together with me dressed and I wouldn't want to in any case.