I have gone back to school myself, though I am not a single mom so I have the help of my husband.
Anyway, Can you find a work program where you work weekends only? I have a friend who is a CNA and works 2 -12 hour shifts between Friday 3pm and Monday 7am each weekend and gets paid for fulltime and benefits. Then she goes to school during the week. Have you considered changing your living arrangements and finding another single mom to pair up with while you both go to school and help each other out, maybe you could cut expenses enough to only work part time, or only go to school parttime. OR, if you own your home and have some equity in it, taking a home loan for a year or two, to cover all your expenses and only work part time while you go to school, and hire a mother's helper to help you out.
OR: the first thought that crossed my mind was why bother with LPN school if you want to be a mid-wife? Go get trained as a certified Doula and then ease into that work while you get your RN to become a midwife.
Good luck with your career, you will be an inspiration to your kids!