Is your wife able to work part-time to help support the bills? I'm sure child care is a concern but you might be able to find a child-minding community group where everyone takes turns minding the children.
I don't know about the climate that you live in but you can try to reduce your electricity and heating costs of your home as much as possible.
I'm not sure if you have any co-ops near your home but they can be a cheaper source of food if you don't mind using your own containers and purchasing in bulk.