I raised my children as a single mum on less than that, but have never had a car, and have always worked within walking distance - as in within 5/6 miles, so could walk at least part of the week - also a teacher so few school holiday child care costs. No child maintenance ever though, not a penny.
I get that money is a limiting factor on your freedom, but it does not have to be a limiting factor on your happiness.
We did camping holidays by public transport, we did free and cheap activities, we did second hand shops.
What I am trying to say is please enjoy life, and take on the doing it on the cheap as a family challenge.
It is hard to explain what I mean, but we were happy, as my children grew up - in the last couple of weeks we have had more than one conversation about this as I am now off work sick, and my children are helping me out, paying my bills, etc
They have both said they have no idea how we did it, had so much fun on so little, and scraped by
More money is always welcome, but I hope you and your children are having a happy life with what you have got and are going to be able to look back on this stage of their lives with affection
xx