Here is another approach to learning and exploring the scriptures.
Assuming that the scriptures are God's stories (as opposed to man's stories) we quickly discover that each of the characters that God interacted with were unique. I tend to believe that the details that God includes in the scriptures aren't accidental or irrelevant.
We often read stand-alone Bible stories to children, especially to small children as appropriate. But as I've gotten older I find that reading all the scriptures you can find about one particular person that God used makes an interesting character study. It might be more appropriate for older kids or for adults, simplified for younger children. It might be fun to take one character and study him/her (making observations) as a class and then assign different characters to different people and have them come back and tell you the observations they've made and how they support with scripture.
The initial study might require more teacher prep than some lessons. You could use books that people have already written or pre-written Bible studies that focus on one character's life but what about reading the stories and just making observations 1) about the person God was interacting with and 2) who God was and how He interacted with that character.
I'm assuming that these weren't 2 dimensional storybook characters. I'm assuming these were real people but scripture is pretty clear that they weren't "perfect" people.
What if this person were a real person (or child) in your class or in your church? What would that look like? How did they "have it together"? How did they not "have it together"? What did they do? What didn't they do? What did God do?
What would be the value of this approach over other approaches? David is an amazing study but you have to be willing to acknowledge the good, and the bad, and the ugly. Some of which isn't appropriate for young children. If we're learning from the good and bad choices of others at what age do we learn and what do we learn about the people in our lives? At what age to we learn the fear of the Lord (the beginning of wisdom) and how?
Anyway....let your imagination run ... as long as it brings you back to worship at the feet of Father, Son, and Holy Spirit - the God who started the story and interacted with these people in the first place . . .