I don't know about the soaking, people do make manure tea.
I think composting would be a good choice, but you do need other ingredients, but not just the spoiled produce. All three (the coffee grounds, manure, and produce) are "greens" in the sense that composters use the term, meaning nitrogen rich, moist. What you need to mix with the greens are "browns" which are dry and carbon rich. Browns would include fall leaves, straw, corn stalks, shredded paper etc. (check out our composting section for more details, lists of greens and browns, etc).
Just be aware that if you are talking about amending a lawn sized area of soil, you will want a LOT of compost. No matter how big a pile you start with (and there is a limit to how big you can go unless you do the row shape, where it is piled maybe four feet high in a long windrow / cylinder shape, which can then be as long as you have material and room to make it) it will cook down to a surprisingly small amount of stuff. Starting this late in the season, you are unlikely to have enough finished compost by spring to accomplish what you need. You are likely to have to purchase some. But keep working on the compost and it will become a steady supply for you.
Best wishes and congratulations on working to actually improve your soil, not just keep pouring more fertilizer on it (which is a dead end in the long run).