The Book of Psalms says that children are a reward and everyone who has them will desire the best for them. This is true of physical or spiritual children. Our children are the future who will continue our ideals or our struggles.
The descendants of Israel are the next generation of what God has promised Abraham, Isaac and Jacob. They should enjoy whatever God promised them through Abraham, provided they fulfill the conditions God asked of them. What does God ask? Only that their life and hearts be turned to Him. The people of Israel have heard how their ancestors accompanied the Lord and they should have learned from that experience, how to keep walking with God.
God can only fulfill His promise to believers as long as they are aligned with Him. God's promise will be fulfilled to us and even to our descendants.
The Word of God says that the offspring of the righteous will be mighty on earth. Do notice the requirement for it to happen; that is, your life must be aligned with His. When our lives are aligned it is an example to our descendants, a guidance of life for them. Therefore, we must instill strong faith values into the next generation, by living in those values now.
God will fulfill His promise to believers as long as they are walking in His ways.