Dear Eric Short Attention Span:
Is someone at home who can watch the kids? Do you have a writing space set aside with a door? If the answer is yes to both of these questions, go into your writing space and close the door. Let your family know that you need to write for however long and ask that they not bother you (unless, of course, the house is burning down, the toaster blew up, or something like that).
If you are the one watching the kids, you might need to put your writing aside for awhile.
Have you thought of writing when everyone is asleep? Sometimes those are the most productive hours.
By the way, this advice is coming from a person who does not have kids and a whole lot of distractions, so I could be way off on my suggestions..