My two cents: I have watched some children growing up over the past few years from a somewhat musical family, and I have noticed that one of the drawbacks of the piano is that it seems to be quite intimidating (it is pretty big), and there is this mountain of quite rigid musical stuff that seems to get laid on the kids by every teacher they have had. There is a formal aura about it. I notice that none of the kids sits at the piano for fun. Only when they have to practice. The guitar doesn't seem to have any of that: maybe because they are all over the TV. It may make more sense for some kids to have them sneak up on the whole musical enterprise casually (of course the best thing is to have a family that plays music together, but how many of those are there these days?).
I was wondering how the experts on child music learning here deal with the formality of lessons with children. I am not saying formality is a bad thing (kids get not much structure as it is). Just wondering. It does seem to turn music into something "special", not homey, ordinary. But maybe that is a folk bias.
yours, Peter T.