You said you're worried that you wont measure up..
Measure up to what? "The work force" is comprised of people just like you, people needing to hack out a living to pay the bills and put food on the table. You run a household! You are already a CEO, CFO, and COO. You are an administrator and manager. You can do any job! Your job as a parent, as a mother, is the hardest job you'll ever encounter. You've already mastered that. Everything else is a cake walk in comparison. You'll be fine. You really will.
Seems to me that you're afraid of the unknown and this is bogging you down a little bit. It's reasonable to be apprehensive. I'm tied up in knots about starting my job tomorrow. But once I get there, and the unknown becomes known, I know I'll calm down. I suspect the same will happen for you.
Now, regarding any feelings you might have about not being there for your kids- I cant help you with that. I'm struggling terribly with that one myself. But the bottom line is I have to work. I have to let go of the guilt and have faith that it will all work out. You need to have faith that it will work out, too.
And- if you dont get offered the job, dont let this affect your self esteem. It simply means you and that particular job and company werent a match. It has nothing to do with you as a person. Keep applying.
Chin up!