I just had to recreate this activity with my own kids! We did this last year and included a 5 year old friend, too. I was worried that my profit ratios would be off but everything worked out perfectly. The 3 boys had fun, learned a little, and then lost interest. But the girls kept going for at least an hour. Now that I've found the price list that I made, we'll have to do it again!
As you can see, each kid started with $14. (I had a ton of pennies and other coins so we used those instead of dollar bills. So I guess the price list should have everything in "cents" instead of "dollars.")
Then they had to decide which tool (toothpick or paper clip) and which piece of land/claim (cookie) they would buy to start with.
The "small cookies" are Famous Amos Bite Size Chocolate Chip Cookies
The "big hard cookies" are Original Chips Ahoys.
The "big soft cookies" are Chewy Chips Ahoys.
The goal is to use your tool to dig gold (chocolate chips) out of your claim. You can only use your tool (or 2, if you buy a second) to extract the gold, not your fingers. (I did give the boys more leeway with this than the girls.)
Once they had a nice pile of chocolate chip gold nuggets, then they would sell it to me. If their gold had too much cookie stuck to it, then I would not buy it from them. They had to go back and use their tools to clean it off some more.
As you can see from the price list above, based on how much chocolate chip gold nuggets I measured, I would give them the corresponding amount of money. And then they could use their money to buy another claim or tool.
Once they were done playing, they used the profit that they had earned to buy some cookies to just eat. The kids learned pretty quickly that just like most of the real gold miners, they were doing a whole lot of work with not a lot of reward at the end. But they still had fun.