CADskin - It's great that you are so sensitive to how your wife is feeling. I agree with FHN that setting her up with exercise/gym/fitness may well reinforce the idea that she is somehow less attractive - unless she herself initiates it.
Here's my perspective, as a psychologist (I think Ballistic was heading that way). I don't know how long ago you quit drinking, but there is a phenomenon related to family systems theory that occurs when dramatic change happens in a relationship. Every aspect of a family relationship is part of a system and tries to work itself into a state of homeostasis, or balance. When something throws that balance off, whether good or bad, every part of the system must adapt. If one member of the family is the "sick" one, every other part of the family adapts to maintain the status quo, good or bad. You were a different person when you were in a band, drinking, ignoring your family. Now you are sober and responsible. Your wife was accustomed to her role managing the family, life, relationships, finances, etc. etc. when you were not there (but there). By becoming sober you've displaced some of that responsibility, and in a way, you've unsettled her. She knew how to manage life when you were drunk. She's less certain how to do it now that you are sober. Her self-confidence has been shaken because you are healthy and well - as bizarre as that might seem. You are no longer the "sick" member, and your wife is struggling to adapt to the new family system.
The key is finding a new systems balance. Talk to her and ask what you can do to make her feel good about herself again. For a long time she was responsible for you and the kids and managing a home without your support. Perhaps now it's college, or volunteering, or who knows what? But you both need to learn how to work within the parameters of your new relationship. Counselling with a therapist familiar with family systems theory could do wonders.