Help! 'Lawn' that is basically weedy wasteland, how do I rescue it?

[Badweekjustgotworse]

Years of neglect and builders who once laid really crap turf after doing an extension have lead to this... see pic.
We've lived here, rented it to tenants and have now moved back in for the next year while we Refurb our family home. The lawn is appalling and as all our current finances are being put into the big house we cant afford to spend any money here, but the lawn is soooo bad it's ruining the garden. We have two small children and I'd love it to be a soft level grass for us to lie out on and play in rather than the concrete hard pitted uneven barren wasteland that it currently is. I'm not a gardener though and have literally no idea where to start.

[Badweekjustgotworse]

Bumping for any late night gardeners out there!

[Enb76]

It looks like it needs some air - take out the moss, go round poking holes in it with a garden fork, scarify and overseed, keep everyone off it for a couple of weeks and keep watering it, mow it when the new seed is about 5". Then come next spring, feed and weed. That's probably the cheapest way to do it to get an ok lawn.

It'll take a year or so to look nice though

[JT05]

All of above, and grow some grass seed in shallow trays. Then you will have some to put in any bald bits.