The origin of this is Chaza”l.
When the Kohein Gadol finished the ahvoideh on Yom Kipur and he was going home, there was a massive crowd accompanying him and people where trying to get close to him to kiss his hand. Many times he couldn’t get home till midnight.
It is reported that the Ari Zal when he arrived home from davening Friday night, would kiss his mother’s hand. The practice has a history. Aside from that, it was often that the Rebbe was sitting and those coming to greet him were standing. Kissing the hand was about the only convenient way to do it. If there is merit to this observation, it would suggest the nature of the relationship was more than simple respect.
The custom of Birchas Habonim on Friday night appears to have been well known and widespread in earlier generations. However, virtually every reference I have seen on the subject refers to the brocho being given by the father. I have no problem accepting that a mother can also bentch children, and would actually consider this something I would invite and appreciate. But I have never seen it referenced. Secondly, even the references to the Ari Zal do not have any mention of preparing the hand to give the brocho. It sounds like a nice thought. Where did you find it?