exercise in limited time
We all face this problem!
In addition to the great advice above, maybe also doing more vigorous things with your kids: chase one of them, play tag, etc. And at work, try to "visit" or borrow things from people far from your desk so you have to get up and move every hour or half hour. Just to get the movement going a bit. And on the weekends, consider going out for a walk or hike with the family, and if they don't want to, go by yourself...and then tell them of all the fun things you saw. It might encourage them to want to go also. And if they do, then you can drive them to a nearby park for an explore. That could lead to more of them, more places visited, maybe to a mini-picnic afterwards every once in a while, and suddenly everyone's loving the Dad and his cool new ideas. "Hey Dad, can we hike up a mountain?" might be just around the corner. It can snowball just like that. Just take that first step.