Master the feet or thighs before moving on. Focus on absorbing and cushioning the ball. Maintain balance with the arms out to the sides at the moment of contact. Practice chest traps with both boys and girls. Sometimes girls need confidence to use this skill.
Trapping is a more advanced soccer skill.
You do not need a soccer background to play with a child. If you show an interest, a child will want to work with you. Suggest, don't insist. Parents should practice only if children are interested and enthusiastic. Use positive encouragement.