Sometimes I feel a little guilty when I lock myself away to work on a manuscript. But that same guilt keeps me away from my manuscript(s) for days at a time. I may steal 30 minutes here, an hour there. But it is hard to write a novel in stolen moments! And even harder (yes, even harder) to write a picture book that way.
So I say, no more guilt. And the same should go for you. Take the time you need to be with your family, but let them know that you also need to take time for your writing. One good way to do this is to create a schedule for your writing time.
My family can count on me spending a couple of hours writing on Saturday morning while the kids watch cartoons. And of course, there are my Wednesdays, which I have all to myself. If you don't have that luxury, try writing one or two evenings each week while hubby (or wife) plays with the kids. Or write once they're in bed or early in the morning.
Whatever your preference, let your family in on the process, and once your schedule is set, be firm! There should always be room for flexibility, but you'll get so much more done if they know you're serious. And best of all, no guilt!