Won't be able to use a reflector, won't have assistants. A tradeoff. Maybe a bit like wedding guys, they just turn up and do the best they can.

This is too large.
http://www.lastolite.com/ezybox-hotshoe.php

I have thought about this. At most, I could pop the flash to the side with a sync cord.
http://www.lastolite.com/ezybox-speedlite-softbox.php

They may spend time outside at later in the afternoon, as it's visiting friends. I could always say that and they would oblige I think. Like late morning or later afternoon, maybe even approaching sunset time and twilight. In these situations, what light modifier do you suggest?