Same with my family, but in a metropolitan area of the Northeast, where we grew up. (Although I don't recall hearing the expression you referenced about the heart, though.)
One of my brothers had kids, and they always addressed adults by their first name. I recall the first time I heard that, I was surprised, as that's not how we were raised. I suppose the social rules may have relaxed over time, but it still seemed a little unusual. I think part of my hesitation was due to the fact that addressing someone as Mr. or sir, for example, sets up an (invisible) barrier of respect -- in the sense that a child doesn't need to assume that an adult is one of the kids. Addressing someone by first name (to me) indicates more of a familiar relationship. That said, my brother's kids certainly meant no harm at all in how they addressed adults, and were always good kids.
