We see Nana once a year. On our 15 hour car ride, I discussed with my children the very simple 2 Rules for our time at Nana's house. One of those rules was, "You will hug Nana generously and without hesitation." The children performed this task beautifully. With glad hearts, they hugged their grandmother, both when she asked and when she did not ask.
As we traveled on, we stopped to visit friends in Dallas. My friend had a very interesting perspective on this. She recounted how her rule for her daughter is exactly the opposite.
"Do not feel obligated to hug your grandparents, great-grandparents, uncles, aunts, or any other schmuck who tries to hug you." (paraphrased liberally)
I respect this lesson in personal space and boundaries. The intentional message of "no means no" is vital for children to learn. Children need to be empowered to feel safe, and help themselves say what they need - whether it be inside or outside their own family!
We joked about the extremes of both scenarios, and agreed that there is always a middle way.