Memorize helpful scriptures as a family project. Anything that reduces fear will increase confidence. Model what you want your child to learn. A father teaches his boy to catch a ball by heading out to the yard with mitts and ball. A mother passes down a family recipe by showing her daughter how to prepare it.
Children learn how to share their faith in the same way.
They need someone to demonstrate it for them. Affirm the Kingdom potential each child has to offer. God has given each of His children different gifts and abilities. He went to great lengths in Scripture to emphasize the importance of each gift. By doing this, God modeled to all parents how to affirm uniqueness and significance.