Someone came looking for Sunday School material for this passage from John 6 (NIV):
"14After the people saw the miraculous sign that Jesus did, they began to say, "Surely this is the Prophet who is to come into the world." 15Jesus, knowing that they intended to come and make him king by force, withdrew again to a mountain by himself."
I did a Bible Gateway search for "Jesus king" Most of the references listed include "kingdom." He was always talking about the kingdom of heaven. Not sure that he was talking about being king.
Then you have Matt 17:25. You have Matt 27:11 and Matt 27:37.
For years, my husband has asked the question, "Do we assume Jesus was a king like every other king or is it that Jesus came being what a king is supposed to be." George got quite upset once to hear a pastor say that Jesus changed when he got to heaven. Our understanding is that He is the same yesterday, today, and forever...
So keep going. Take your study and see what the gospels say about Jesus and king. Search the OT and the rest of the NT, too if you want. I try hard to make observations and ask questions. The waters get murky when we start drawing conclusions. The waters get dark when we teach those conclusions as scripture. We comment on the scriptures and become the primary voice instead of stepping aside so the scriptures can be the primary speaker and speak for themselves - Himself. If I fail, tell me.
Prayerfully go searching, go looking and see what you find...Then ask, how can I share these stories about God with children? What does God say about kingship and Jesus as king? Do they say anything?
You'll want to share what you discover but you'll also want to give your kids opportunity to share what they discover. Separating the way all of us have grown up to understand "king" from what Jesus says and what He came to show us about being "king" will be the hard part.