My daughter and I use a devotional Bible book that we both really like. Actually we have a few. My daughter is a bit younger than your target audiance but the principals are probably the same for the most part. Taking things from the Bible and relating them to real life is a key thing. Things like sharing, patience, caring, forgiveness, and many more. For a easier list you can look at these passages. Find things in the Bible that teach them and do devotions based on them. They are the core principals of being a Christian.
Philippians 4:7-9 And the peace of God, which passes all understanding, shall keep your hearts and minds through Christ Jesus. Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things. Those things, which you have both learned, and received, and heard, and seen in me, do: and the God of peace shall be with you.
1 Corinthians 13:4-8a Love suffers long, and is kind; love envies not; love vaunts not itself, is not puffed up, Does not behave itself rudely, seeks not her own, is not easily provoked, keeps no record of evil; Rejoices not in iniquity, but rejoices in the truth; Bears all things, believes all things, hopes all things, endures all things. Love never fails.
