Be sure he understands sin. Many children will not admit to being sinners. Make sure he can name sins and admits to being a sinner. Be careful to sense attitude and look for conviction. Be certain that he understands salvation is by faith, only.
Many children think that other things are necessary for salvation, such as baptism, good works, etc.
Never let a child go until he knows that he is saved because the Bible says so. It is not a thing based on feelings or emotion. Worship is the loving response of an individual's heart to a consciousness of God's person and presence. It is a reverent devotion, a service, or an honor paid to God. Worth-ship refers to God's worth and worship is appreciating God for who He is.