I think it's great you're considering your child's health--Moms are so overworked, too, and it's really easy to let diet and exercise slip by the wayside when there are so many other things you have to think about.

I would encourage play more than anything (rather than explicit exercise). Exercise today has such a negative connotation-it's something you *have* to do, not something you *want* to do. Playtime, however, we all love. Get your son to romp around outside with a dog, if you have one, or go on walks together. Sure, it's cold, but once you and he get bundled up and moving, you won't even notice (unless it's just absolutely intolerably cold). Once your son sees you out there moving around with him, he's much more likely to enjoy it. If it is too cold outside for you, jump rope indoors (just watch for those ceiling fans!). Dancing around is fun, too. I'm not sure how old he is, but when I was a kid, I loved being chased, and running through the house for a bit always got my heart rate up.

I wouldn't worry too much about his "belly fat." Growth spurts and hormonal changes all can make a kid's body do strange things, and body types are not always genetic. Focus instead on making sure he and your family are taking in lots of leafy greens, vegetables, and healthy cuts of meats while being active, and that will send a much better and clearer message to your son than chiding him to exercise and lose weight. The goal is to encourage him to make healthy decisions, not feel terrible about his body or anxious about exercise. If he sees you doing those things, healthy living won't be so strange to him, and he'll be more likely to follow suit.

You didn't say how old your child is, but he (she?) might be interested in sports like soccer, gymnastics, basketball, etc. which would be good. He should also have PE at school which is helpful.

Your child should never be drinking sodas or other sugary drinks, and desserts like cookies and cake should be a rare treat.

You can play catch with him after school, ride bikes, or hike. Even a walk after dinner now that it's light later is worthwhile.