Consecration of a Child to Mary
Holy Mary, Mother of God and Mother of all faithful, I place my little child under your mothering protection. To you I completely consecrate him - body and soul. Take him under your care and keep him always. Protect him in his infancy and keep him sound in body and mind. Guard over his youth and keep his heart pure, his thoughts ever holy and directed to God and spiritual things. Protect him always throughout life - in his joys and sorrows, in his dealings with others. Always and in all things be a true mother to him, Mary, and preserve him. I commend him entirely to you. Remember Mother Mary, that through this act of consecration he is by a special claim your child as well as mine; guard him and keep him as your property and possession. Amen.
-- From a Catholic Mother's Manual prayer book (1941) by A. Francis Coomes, S.J.
The lovely mama at JOYfilled Family shared this beautiful prayer of consecration that her priest uses...
ACT OF CONSECRATION OF A CHILD TO THE IMMACULATE HEART OF MARY
Blessed Virgin Mary, * Queen of Heaven and Earth, * to your Immaculate Heart,* the channel of all graces, * we consecrate this child * whom we have received from God’s goodness. We offer him [her] to you * that you may present him [her] to Your Divine Son, * that you may take him [her] under your loving, maternal protection,* that you may preserve him [her] from dangers, * that you may keep him [her] from all sin, * that you may make him [her] grow in piety * and in all virtue * so that he [she] may always be worthy * to call himself [herself] your child. May he [she] grow daily in wisdom and in grace, * may he [she] go through life having you always as his [her] refuge and mother. * May all virtues shine in him [her] * and may he [she] never offend your maternal Heart. May the Eternal Father always look upon him [her] with delight * and see in him [her] * a ray and reflection of your Immaculate Beauty. And as today he [she] gladdens our home, * so may he [she] one day gladden the Eternal Home * which we pray will be his [hers]. Amen.