I would have said please. No one would have asked me "what's the magic word." When "Please" and "Thank you" are standard and common in a family, that seems to be a good thing.
My husband and I have been married for most of the 32 years we've been together. When we were a young couple, friends of ours commented a few times that we said "please" and "thank you" about the smallest of things. We did it when no one was looking, too. About a tissue, or a glass of water, or just any little thing. Opening doors. And because of that, we never "taught" our children to say those things, but they did, and they do, because they've always heard it.
Thanks for the feedback! Not sure what the question was that you had. I did end up saying please and we do use it between Rob and I and with Martel and Greyson. They often use it as well. Like you, we have not "taught" them to say it. Most of our unschooling friends do the same and I never hear "What is the magic word" from anyone in our circle of friends. And I hear their children use please at our house often. In writing about the experience it was about the feelings it evoked in me. The situation brought me back to my childhood when shame and humiliation at the hands of teachers or parents was much more commonplace in my life. And, I think at times I might forget how that feels because it is more far removed from my experience now. The power that adults' words have, both positive and negative, sometimes gets lost.