Hi E.,
My situation is a little different than yours, in that my job is not sales based and I work full time. But I know what you mean, completely and exactly, about trying to keep all the plates spinning! It's hard to have 2 jobs - that of mom, and that of whatever other career you choose. No matter how much you earn, how little you're out of the house, etc, there will always be resentment by your kids and your husband when you are out of the house working for someone else! They want you ALL to themselves!
I have tried to help my girls understand (they are 5.5 and almost 3) that mommy loves her work, and I will explain to them some of the things that I do at work (in simple terms that I think they can understand). My feeling is that although the care and upbringing of my kids is the most important thing I will do in my life, me having a job, staying sane, and keeping us all from living under a bridge is just plain necessity, and they've got to understand that.
At the end of the day, if you truly love staying home with your kids and don't so much enjoy sales, try to get some very part-time work doing something else so you can get out of the house every so often and have some grown-up time. Especially in this economy, there is demand for intelligent people who do not want/need to work 40 hours per week. Or if you do not need the extra income, you could try volunteering at your 6-year old's school. With your background in early childhood education, I bet they would love to have you help out!
Good luck to you. I know it's hard. You're not alone; I think most of us who are juggling career and family are right there with you!