I'm going to ask you some hard questions. I do it with love. If you are able to stay home I celebrate you for that. But here are a few facts to consider.
You say that you are providing the childrens insurance? That seems pretty major. It may not make sense to only bring in $400 per month now, but those insurance benefits are going to cost another $400 at your husbands job - if available. So, your contribution to the family is actually $800.
If they have insurance at your job, they also probably have retirement benefits. Is your husbands retirement account going to be enough for both of you? If you don't pay into Social Security now, you may not be eligible to draw any when you get older.
What you make now will increase. You will get raises. Maybe even promotions and new opportunities. But you have to be in the building for any of that to happen. Are you going to go to work when the kids go to school full time? You will be 5 yrs behind everyone else that has been working. Industries change, technology changes. It will be much harder to go back to work with a 5 yr gap on your resume.
I pay $600 per month for both my children and they are well cared for. You can find more affordable care.
Like I said earlier, all out of love. You do what's going to make you and your family happy and stand by that choice. If you do stay home, I suggest taking online college courses just to stay current in your field and so when you are ready to go back to work, you have a few more feathers in your cap. Best of luck to you and your little ones.