What about the option of alternating riding and driving. Ride in one morning and the drive home and then drive in the next day and ride home. This wouldn't increase the number of rides, but let you ride more days. Perhaps, you could increase the length of the ride home to increase the total miles for the week.

There are several good options above too, but you and your spouse have to find what works.

Off point, but the final mile issue of not being able to ride, but it is ok to walk seems odd.

Also, consider looking into "travel reduction" or "commuter reduction program". Often if a business has a certain number of employees they can use these programs for their employees. I would think an industrial plant could benefit from being able to say they use environmentally friendly productions methods AND even use/encourage travel reduction amongst employees.
Sorry for the last part being a rant. It doesn't help with riding more, but it got me fired up. Maybe I should go for a ride.