I am in a very similar situation: Mortgage, kids, wife and in an almost failing startup. First, you need to know how much risk the wife can stomach. Second, the money does not matter to children; they may be better off if you have more time to spend with them. Third, always have small contracts on the side to balance the startup losses. Fourth, it is important that you contract to other companies, instead of being employed. This will help with the small contracts, but also allows you to own the copyright you build for the startups; maybe not directly useful to you, but adds to your personal library and makes you more productive to your customers.

Good luck!