Should my husband and I change careers?

My husband and I have struggled financially almost our entire marriage of 14 years. My husband, juggling different jobs with no college degree and me being a school teacher, decided to have a child 5 years ago. We both thought it was important that I stay home with our child for the first 5 years. It was a financial struggle to say the least, but we feel it was worth it. Now, I am back to teaching school making 48K and my husband has had a steady job for 4 years making around 70K. We are finally doing better financially but we both hate our jobs. His dream would be to go back to college and become a coach and my dream would be to start my own local business. We are behind financially in savings, for our son's college fund, and for retirement, and we are both close to 40 years old. Would it be stupid to try to change careers at this point and take such risks? Especially in today's economy? Should we just suck it up and stay our course even though we are miserable in our jobs?