Hi,
that's a lot of land, you'll have a lot of fun growing there
i guess everyone here will give all sorts of advice how to tackle this. on a plot this big there is no shortage of soil and you want to save yourself the effort of painstakingly separating weeds/roots and soil.
I have a small plot in my garden and it was all covered in grass, huge dandelion, trails of nettles.
the best advice i can give is separate the land into sections you can work on each day.
to dig out those weeds and grass, best would be to get the fork, dig huge clumps of soil out and turn it over exposing it to the sun. don't spend time separating the soil and roots, do that later. quickly work your way from each clump to the next.
once the sun dries out the soil then beat the clump of soil with the back of the fork and hopefully it will loosen the roots and weeds and you can bin them all or just beat the dry soil off and as one big clump of weeds and roots just bin it in bags. alternatively to save time doing this you could just put the lot in black bags, on a trailer and take it to the local recycling centre. i know its a lot of soil to throw away but there is plenty there anyway. if its clayish then you can get sharp sand and hire a rotivator, work it in and hopefully soil will be workable over time.
in terms of roots you can pick them out with a rake but if there on the surface then the sun would do the job of drying and killing them off.
Huge dandelions may not come out with ease so spray weedkiller on them.
Health wise ensure you and your kids drink plenty of water and cover yourself from the sun, as its getting quite warm out there.
Good luck and have fun