Scripture is being read and the congregation listens. Some simple guidelines for church may allow you to relax. Quiet work like looking at a book or coloring or drawing is ok during the Liturgy of the Word. A soft noiseless toy may help. Some movement is to be expected from children.
Children love gestures.
Teach them to make the sign of the cross, to bow at the cross, and help them to notice the gestures and symbols in the church. Encourage older children to follow along in the service leaflet and prayer book. Teach the mystery of faith, the Lord's prayer, the peace, and other parts of the service to your child. Strategically placing mom or dad between siblings is sometimes all that is needed to help a child settle in church. An entire service hour is too long for many children to remain quiet and calm.