Get rid of her.

(Just kidding. That was a line from a golf movie ...a pro complained to a supporter/sponsor about trouble with the wife. The sponsor simply said, "Get rid of her.")

Actually I'd say get a Burley and carry the kid with you on the day-off ride. The wife may actually get interested enough to try it out herself and come along. A problem I had initially was that the family went too slow. I just loaded myself down with burleys and trail-alongs on a singlespeed so that I got a good workout going their speed. Now all my kids are fast and the young ones love to go biking with me. (Older ones are teenagers and, by definition, hate their parents)