It is customary to bless your children at the Shabbat table if your are Messianic Jewish or Jewish. Shabbat is Saturday. But any day that you set apart for the Lord will work. In our family my husband blesses the children every night before they go to bed. He holds them in a hug and puts his hand on their head. He ends each blessing with the words “In the name of the Father, Son and Holy Spirit. Amen.”
According to Genesis 48:20, the traditional blessing uses Joseph’s sons and the matriarchs. (We do not do this.) Parents may add their own blessing or additional words of love and appreciation of your children. My husband blesses each child individually, but you could bless your children as a group.
Grandparents can bless, too. Or mothers could if they have a husband who will not.
Traditional Jewish blessing:
The Lord bless you and keep you.
The Lord make his face shine upon you and be gracious to you.
The Lord lift up His countenance on you and give you peace.
There are a lot of books on blessing your children and the father’s role in giving blessings. On the other hand, there is also a lot on this subject online. You could do a search on it and pull up a storehouse of information!