Yeah, so all this just points to an opportunity within the ebook realm to create a more refined experience. It does not necessarily mean physical books are superior in any way.
I'm a parent, too, but to me the fear of giving children too much "screen time" is anachronistic in this day and age. Not to say that screen time SHOULDN'T be limited, but the reasons for that are primarily because of the passive nature of, say, watching videos where images on screen change quickly. There is evidence that this sort of constant passive entertainment can erode attention spans. What we're concerned primarily about is !) instilling self control, which in and of itself has nothing to do with electronic devices, and 2) exposing our kids to a variety of stimuli and not just whatever appears on a screen. But again, this latter point is important irrespective of whether we're talking about electronic devices, legos, or barbie dolls.
As to buying physical books being a great bonding experience, I agree, but I think it's also beside the point.