When we pray with young children, we take care not to put prayers into their mouths but, at the same time, to give them a "language of prayer." 3-6 year old children spontaneously pray prayers of thanksgiving and praise ("Thank-you, God, for our families!";"God you are so good!" ;"I love you, God!"). Petitionary prayer is foreign to their tongues, therefore we are careful not to introduce petitionary prayer too early. Young children enjoy their relationship with God who provides for all their needs.
We provide them 'rich food, but not too much' to feed their prayer language. By this we mean, we give them a word (eg. "Alleluia!"), a phrase ("Glory to God!"), or a verse from scripture ("The Lord is God and he has given us light!"). We speak this word or phrase with reverence, and then we are silent. We allow the Holy Spirit room to move. Then we might invite the children to speak what is in their hearts, if they wish, but we do not force it.
Try this with your child. Light a candle. Open the Bible with reverence and awe. Turn to a psalm of phrase and read one verse (eg. Psalm 46:10, Psalm 27:1, Psalm 23:1, Psalm 43:4). Sit in silence. Repeat the verse. Wait in silence. Invite your child to pray aloud (eg. "What can we say to God?"; "What do we want to say to Jesus?") Wait again--longer than is comfortable! If your child says nothing, don't worry. Spoken prayer is just the tip of the iceberg. Only God knows what is taking place in the heart. Say, "I love you, Jesus," and then invite your child to snuff the candle.
Read more in this article found on the US website.