Not childish no. But interestingly God and Heaven are explained to children when they ask difficult questions concerning life and death. They can easily comprehend the idea that a magical being is responsible for everything and we don’t need to think too hard on existence. It’s also great for controlling them (ie if you’re bad you’ll go to hell!) Some children grow up and make more mature assessments on existence – not necessarily discounting God, but at least able to more sensibly define Him/Her/It. Others find it hard to question their cultural upbringing. Things we “learn” as a child are sometimes difficult to unlearn and are further reinforced by the older generation who were also unable to question their own teachings as a child.
No. However, in the book of Matthew, Jesus was asked by His disciples “who is the greatest in the kingdom of heaven?” Jesus called a little child, whom he placed among them. And He said, “Truly I tell you, unless you change and become like little children, you will never enter the kingdom of heaven. Therefore, whoever takes a humble place – becoming like this child – is the greatest in the kingdom of heaven. And whoever welcomes one such child in my name welcomes me”. (Matthew 18:1-5) Hope you understand the difference between childish and child-like.