You are so lucky to have a wife who wants you to bike commute every day.
I remember the very first time I rode a new bike home (from WalMart), my wife pretty much followed me home in the car. She insisted that I ride the bike on the sidewalk. She stopped to yell at me when I got off the sidewalk. She was fearful that I'd kill myself if I got off the sidewalk. She really didn't want me to bike commute. It was embarassing, but endearing. She was just worried.
Things have changed. Now she finds ways to make it seem more practical for me to ride the bike. I think she's proud of me for this.
Of course, you've got a far longer commute than mine. It seems reasonable that it would take a while to build up to that distance. I'm sure you'll get there if you build up carefully.