What does it mean to have child-like faith?
Child-like faith is imagination. And imagination is the door into the spiritual realm. In this sense, all faith is child-like. Faith is the willingness to see what is unseen. Child-like faith is the courage to ride your imagination as far as it will take you. It is the refusal to place any bounds on one's journey into the imagined. It is indulging whimsy. It is being utterly un-self-conscious. It is doing stupid things, making a fool of yourself, all while taking in the world with breathless wonder.
When I watch my boys play battle with their LEGO creations or my daughter dress up her dolls, I don't need to remind them that it is all pretend. Because it is real. The truth is their fantasy world. They delight in their toys because they perceive an unseen reality beyond the plastic pieces they manipulate.
When my kids have nightmares, it is not helpful to tell them their dreams aren't real. Because they are real. The fear is real. The monsters are real. We don't have to explain to kids that more exists to this world than what we see with our eyes. We don't teach children how to use their imagination. They are born knowing. We only teach them how not to use it. Or not to use it all. That's how they become grown-ups.
When we tell a child about Jesus and how He died for our sins, we don't need to assure them that the act is historically true. They feel the reality of the cross like the warmth of the sun. The challenge is for them to keep trusting when their faith is constricted by worry, fear, and all the evils and struggles of life.
Naïveté is only dangerous in a dangerous world. Belief in God amidst a fractured existence requires boundaries for protection. That's why most apologetics - logical, historical, and theological arguments for the existence and character of God - are helpful. But in the end, they're only boundaries that may or may not funnel you towards Him. In the end, we only approach God through our imagination. You cannot experience what is good and true unless you step off the cliff.