This is pretty hard to answer b/c I don't know how old your kids are and a bunch of other details. I'm applying right now. I have two kids 10 and 8. I've been doing my post-bac work at the same time my wife was working on her graduate degree in nursing. I work full time to support the family. So I have great empathy for your situation. It's pretty tough.
I did not find the pre-med coursework that difficult, but I'm an engineer and I've been studying and working in the sciences for many years. You have a BA, and it sounds like you didn't take much science. It's hard for me to tell how hard you might find it, without knowing more about you. Whatever the case, you are in for a lot of work!
Here is how I would approach your problem. I would start my post-bac with 1 class and see how it goes. If it works out okay and you feel you still have extra time, add another class the following semester. This approach will allow you to ease into your new schedule (and subjects) and hopefully not over-commit and crater. Med-school is too competitive to chance having a bad semester/qtr.
Make sure your husband is on the same page as you, and is willing to help in concrete ways. You do not want to start this process if he is not behind you 100%.
This will no doubt extend your post-bac program significantly (1 year?) but your workload will be more manageable. Your grades will be better. By the time you go to medical school, your kids will be older and require less attention from mom, and you'll still have a husband
If you have any more questions you want to ask me, PM or post. I'd be happy to share experiences from my little corner of hell. Seriously though, All the tribulations not withstanding, I haven't felt this energized in years... Good luck!