working Moms vs Stay-at-home Moms

I used to be a stay at home mom, I worked while my kids were at school for a couple of years, but that was about it for a long time. Now my kids are all older, the youngest is nine, the oldest 15, and I'm trying for a new job that will mean I will be out of my house for 10 hours a day. My current job is short on hours and even when I get 40 it's stretched out over 6 days and the hours are very flexible, which is why I decided to do it in the first place. My husband has a very flexible schedule, and so far things have worked out well, but this new job, if I get it, (and I want it) has me worried. I would have set hours and be home for dinner every night, but not home when my kids get home from school most likely. They get off their bus around 4, so they wouldn't be home long and the older ones are competent babysitters who know the rules but I still feel a bit of trepidation. Probably because for a long time I felt most mothers didn't have to work outside the house and should have saved the money they spent on day care and stayed home. I am working because I have bills to pay, not because of some misguided "men are evil you must take care of yourself" thing. I have gotten jobs, even after being out of the workforce for several years, with very little effort on my part. So I know that at least some of the "keep working or you won't get hired again" is, to a degree, false.
Now I'm faced with the fact that I need to work at this time, and while I know I have good kids and a solid support system of a husband who works from home part of the tie and who can arrange his days around emergencies, (not that I couldn't) and most likely be home when they get here, I still worry. I'm the mom. I'm the one who has 15 years of running a household. How can he do it? Why am I not doing it?
I have to get it through my head that now we do it together. Dear Husband can do everything in the house but laundry, and all the kids except the 9 year old know how to do that. All the kids have chores too, it's not like I do it all.
Most women who work look at their career and family and think they have it all. I can't help but look at my family and wonder, if I get this job, what I'm going to miss.