I did this for a while last year when it was conducive in my schedule. I would get up a little earlier, do 10 minutes of Yoga. Then, I would take a walk at lunch (which actually ended up being about 20 minutes...), and then, when my daughter came home from pre-school we would do something active - like play hop-scotch, or ball, or soccer. We would play those games for about 15 minutes or so - until her attention wore off of it LOL!
It actually worked pretty well to keep me in shape. I was a little worried at first because I'm used to working out vigorously for longer periods of time. Now, I'm back to teaching dance three times a week, so that's my workout... that and hiking on the weekends.