I, too used to be a runner and Vampy is right, you start off small. His suggested exercise method is sensible.
If you don’t have anyone minding the children at all … how about a gentle then brisk walk first with the 6 year old walking with you (depending on how she goes) & the younger one in the jogging stroller, until the 6 year old attends school. (I’m not familiar with the starting age of attending school in the US). Then increased to jogging, when you only have the young one in the stroller.
