I'm sorry that you're feeling this way - having to compromise on health for a job is never fun :(.

I don't know anything about your specific circumstances, but depending on what your daily route to work looks like, you might be able to make it work with a special bike. There are fast cargo bikes which fit two children and could even be outfitted with an electric motor (e.g. http://www.larryvsharry.com/). Or the obvious solution, road bike + trailer.