I too think the 250r is a good idea for commuting (most of my miles).
As far as convincing the wife, I think that taking a safety course (MSF curricula) from an approved organization would go a loooong way in convincing her that you will be safe. Do that before you buy the bike, though, as they lend you a bike, helmet and gloves, and you get to take the course in one of their motorcycles. That way you find out if you a)like riding a bike, or b)are apt to ride a bike, before you make the investment on your own bike.
Also, talk to her about how motorcycle gear (helmet, jacket, pants, boots, gloves) can help in the unfortunate event of you dropping the bike, and get yourself fitted with the right gear for you.
Once you take the course, decide that you do like the sport, get the bike and gear, go out to a clean, empty parking lot to practice what you learned in the course and let her know that.
That will put her mind more at ease.