Blessing of the Children: Introduction
It is customary to bless children, young and old before beginning the Friday evening Seudah. The flow of Divine beneficence and blessing which comes with the beginning of Shabbat makes it a particularly auspicious time for such blessings.
Both hands should be laid upon the head of the child to signify that the blessing is conveyed with complete generosity of spirit.
Although there is a customary text, each parent may add his own blessings as he sees fit. (Bet Yaakov)