["I really, really need to leave my job because it's making me miserable, but I'm afraid to make a big change.  I'm worried about financial stability for me and my kids, and nervous about leaving a known quantity for an unknown."]
I feel for you. My girlfriend is in the same position. Luckily we don't have kids to complicate things, but her job wears her out and it doesn't seem like she can physically or mentally keep up with it. Kids just make it so that you feel you have to do it until you die, no matter what.
I'm afraid to leave my current job (which I hate) because I might not be able to find work that I enjoy that pays well enough to live on.