I understand that you are in a time of transition and you have to do what you have to do. I would encourage you to be honest about the situation though and keep a careful eye on it.

There is quite a bit or research of the effect of parental depression on children and it is a real concern. http://articles.latimes.com/2010/mar/15/health/la-he-depression-20100315

My suggestion would be that you have a real plan for the long term here. How long can this go on before some change will be made. It may be worth thinking about other part time solutions or about other options to help your coparent get what he needs to feel better.