You start with the different properties of stones. If you have flint, obsidian, granite, quartzite, gypsum, and calcite in your region -- find them together. If not, buy them. Teach your kids about their different properties, and how they were used to make hand tools.
Then, the different properties of woods. Hard, soft, green, etc. Show them why ash and hickory (and especially negatively buoyant cornus mas, if you can get it,) make much better tools than pine. Make wooden spears and harden their points in a fire you make with stone tools.
Then integrate the two -- use stone tools to make other stone tools, and combine stone and wood into wooden-handled stone tools. Make bows and stone-tipped arrows, and use them. Go foraging with the children, and teach them how to cook vegetables, fish, and meat over an open fire. (Note: Beware mushrooms unless you really know what you're doing.)
In short order, the children will understand how men have lived for hundreds of thousands of years. Then they can advance into copper smelting, pottery, building carts and canoes, making nets from natural fibers, writing on clay tablets, and so forth...
I feel that, as with math where the optimal method is to start with Euclid and then progress through the ages, one ought to learn to be in the world by moving through man's stages of development. At 4-7, they're in their prime for traipsing around the woods and making stone tools.