I do think it's unfair to say the OP needs to look at the long term, it's all good and well if you are in a family that can make a loss and still manage fine, but while many families can cope on one wage, going below that one wage can cause problems.
I would look at other solutions like other childcare options (a nanny 2 days, DH working on Saturdays and having one day off in the week, your nanny doing 2 long days should be cheaper than paying for 3 days at nursery for 3; or nurseries/childminders closer to DHs work, losing that commute time hit; or looking for other jobs with more flexible hours) before giving up the idea of work altogether.
But ultimately, if it's going to not even make a profit but also cost your family money for you to work, you do need to weigh up if that's going ot be worth it to make a profit in a few years time, if you'd be likely to get back into work in those few years etc.
Skipton - the OP has already said their finances are shared, if the money she brings in is less than goes out in childcare and commuting costs, and her DH earns more than hers, then calling it a shared cost doesn't make a blind bit of difference to the fact that whatever she does, they are going to be living off her DH's wage (and in her case, her working will mean they are living off less than just her DH's wage as their joint childcare costs will be the same as all of her wage plus a bit of his!).