This is a simple prayer I pray over my children as I put my little one to bed, then over everyone else on my daily prayer list:

Father I put my children in Your hands and ask for Your protection as they sleep. I speak the peaceful sleep of Psalm 4:8 over them. Assign guardian angels around, over and under each bed. Put a wall of fire around their bed(s) as stated in Zechariah 2:5. I forbid any human (witch) or demonic spirits to attack them in their sleep. I bind night terrors, nightmares and any physical ailment that will interrupt their sleep. I loose shalom peace over them. Visit them in dreams, Lord. Protect my children in their sleep. In the precious name of Jesus Christ I pray, amen.

Parents, if your child has trouble sleeping or suffers from nightmares simply anoint your child nightly until you notice an improvement.