When they ask about the stones . . .

Go over before the ark of the LORD your God into the middle of the Jordan. Each of you is to take up a stone on his shoulder, according to the number of the tribes of the Israelites, to serve as a sign among you. In the future, when your children ask you, 'What do these stones mean?' tell them that the flow of the Jordan was cut off before the ark of the covenant of the LORD. When it crossed the Jordan, the waters of the Jordan were cut off. These stones are to be a memorial to the people of Israel forever. . . . Joshua set up the twelve stones that had been [a] in the middle of the Jordan at the spot where the priests who carried the ark of the covenant had stood. And they are there to this day. - Joshua 4:5-7, 9

Then Joshua, together with all Israel, took Achan son of Zerah, the silver, the robe, the gold wedge, his sons and daughters, his cattle, donkeys and sheep, his tent and all that he had, to the Valley of Achor. Joshua said, "Why have you brought this trouble on us? The LORD will bring trouble on you today." Then all Israel stoned him, and after they had stoned the rest, they burned them. Over Achan they heaped up a large pile of rocks, which remains to this day. - Joshua 7:24-26a

They were picked up from the river bed, exposed for the first time to sun and air. The stones of the river bed settled and secure in water remained always dry. What is God comes from the deep.
When your children ask tell them, "You are God's because you have come from the deep." As the stone is dry our life is from the deep but the deep does not penetrate entering our sanctuary though God is our sanctuary and perhaps God is the deep. Tell them also if you want to look for God then look to the deep. Holiness is deep and perhaps the deep is holy.

They picked stones in the valley and hurled them at Achan, his wife, sons and daughters. The stones met with the soft resistance of flesh bloodied with life but dry inside, always dry, purely dry. Gather the stones and when your children ask about them, tell them, "God possess all and God takes what is not gift. God takes all those that take as God takes. We have not God's eyes though we extend our reach as though we can possess. What God has given can be received. It can be received because God has given. What you take, God takes back, always even if it takes longer than Achan. You will feel the stones of greed, hatred or age and these stones will shake loose all that your hands grasp. And things will return to God as they already were."
Tell them that . . . when they ask.