BT:
I'm seriously thinking about getting a Viaggio to toodle around with my kids (5, 9 and 11) and possibly my wife. You mentioned going out with your 6 year old. Are you going to need to make any mods to do that (e.g. child stoker kit or crank shortners)? My youngest is pretty big for his age, but I don't think he be tall enough.
Unfortunately, the bikes are sold out at Amazon. I hope they come back. Seems like a great way to get into tandems.
SHP