Although it may take awhile to convince your wife that the Leica would be a great option for you I do think you are on the right path. Much better to convince her of the Leica to start with than to convince her of something less expensive and then realize you still want the Leica.
I would start by emphasizing the fact that it is a "people" camera and that it will be great for documenting the family. With the right lenses flash isn't necessary and focusing a rangefinder indoors is arguably easier than working with other cameras. Then move onto the service life benefits. A Leica will last for a very long time. You can use it to take photos of children, then grandchildren and finally, even your great grand children. It really is an investment in your future. Finally, emphasize the value. Face it. Though the camera is expensive to start with, given some occasional service, it will probably outlast you. Unlike digital cameras that are frequently tossed out in 5/10 years or so, these cameras keep on taking excellent pictures.
There...if you can't get a good start with that then you need to take a debating class.