I have been following this thread and here is some insight from a competitive runner, father of three, and demanding career.
I think the best advice on here has been roll with the punches. With three children and a full-time working wife that also has running aspirations, I have had to compromise on my running, meaning no more 120+ mile weeks, let alone 80-100 mile weeks.
This past year with a move into a pretty demanding job, I wake at 5:30AM to help my wife with the two little ones (she takes them with her to work to drop at a local daycare) and I prepare my eldest for school. I can't run in the mornings, so I run at lunch up to 1hr. I get home at 6PM and that's when my wife is able to run.
Once the kids start track/soccer/softball/cheerleading, I meet my wife at the location after work and then she goes running and I will run again after practice, so on those days I double, although they are very late nights.
So, the past year has been between 50-80 miles/week with an emphasis on the weekend long run. The great thing is that I focus on quality and staying healthy and have run some pretty solid races, although I know I haven't done the work to approach sub-14:50 on the roads right now like I used to take for granted, but aerobically I have gotten stronger with up to 4hr long runs.
The great news is that as your kids get older, more opportunities to run arise. This upcoming school year I will have two out of three in school, so that might free up the mornings to run as well. The other major contributor to running would be buying a treadmill, but we are both averse to treadmills, although they would be a blessing in the winter.
Soon you will be able to go from 50 miles/week to 80-100 miles/week in no time. Just embrace the 40-60 mile weeks for the time being.