How does your wife take to matters like these, and trans issues?
Based on my experiences with my mother and father, my father knew first and we didn't tell my mother out of fear of how she would react. Then when she found out by accident through my father, then everything blew loose in the worst possible way.
I know I had a bad experience with it, but I hope it is not the case with you. I would plan for the worst, hope for the best. If confronted, it's best to be honest and straight up. I hope all goes well, and we are here to support you.