First of all, good for you for wanting to take the steps to a healthier lifestyle and getting back to your "ideal" weight.
My son is 5 years old and I've been working out and eating pretty well since he was 8 mths or so and I still have a not-so-desirable stomach. It has definitely gotten better over the years, but not what I want. I find that when my diet is clean, I feel better about my stomach.
As for what you can do to get started - move!! Anyway, anywhere you can. I just responded in another thread about the Body For Life program. You might want to look in to that. It is really good for beginners.