I might get flamed for this but to answer your question, I would get more childcare before taking medication.
I suffered from chronic depression in my 20s, I never sought treatment until I basically had a breakdown and had to see a psychiatrist. Having gone through this treatment, I am really sceptical when a GP sees someone for, what, 15 minutes and diagnoses depression and prescribes medication. My psychiatrist said he would need to see me at least 4 times before he would make a diagnosis, as there are so many different disorders that can produce similar symptoms. Even though I had tried to kill myself he did not want to assume I was depressed. He did offer medication if I felt I really needed it to stabilise myself, but I did not take any. I had six months of counselling and have been in really good shape ever since.
I have had a lot of friends suffer from depression and take medication and I know it saves lives, so I am not anti-medication. If you think it will help then by all means take it.
At the same time I know people who have really suffered from the side effects, which is why I think it's not a decision to take lightly. I don't think it would necessarily help the state of your relationship if your libido disappears.
But it does sound like more child care would really help in your situation, and making some of the other changes you talked about, taking a holiday. If you do all that and you still feel down, then you can always start taking the medication. It's not really an either/or question, you can get more childcare AND take the pills.