After that whole generation had been gathered to their ancestors, another generation grew up who knew neither the Lord nor what he had done for Israel.
It is very dangerous to assume the next generation (including children and new believers) know what we are talking about when it comes to living life as a Christian. What ends up happening is that we communicate how to live the christian life (attending church, prayer, reading the bible) but often miss out the reasons why we do those things. Imagine a child asking you "why?" over and over again - why do we go to church? why do we sing at church? why do we pray? why should I forgive other people? why should we give money away? It probably wouldn't take us many of those questions to end up with the answer - "because that's what Christians do", assuming they know the motivation of the gospel because they've heard it before.
When that happens, it doesn't take long for people to stop going to church, stop praying and stop reading the bible because they didn't really know why they were doing it in the first place.
It is important to talk about how we live our lives as Christians, but it is absolutely essential that we communicate why we are interested in any of that stuff in the first place - the gospel.
We go to church to join with others in praising God and be reminded of who He is and what He has done. We pray because we still sin and need to repent and ask for forgiveness. We pray because we need God to change our hearts. We read the bible because we want to know God more. We were enemies of God and yet He still loved us, sacrificing His son that we can be reconciled to Him. That is why our lives are orientated around Him. That is why we want to spend time with other Christians, serve other people, be generous with our time and money and share the good news with others.
These are not the only answers to these questions but they are an improvement on "that's just what Christians do" because they at least begin to communicate that being a Christian is about more than just behaviour.
One generation shall commend your works to another, and shall declare your mighty acts.