I'm not sure what to say about 3-day vs. week-long. We know week-long worked last year; 3-day seems worth trying, because, if it works well, it'll allow the material be accessible to a much larger set. We'll give you the best three days of stuff, but there'll be less total stuff and less chance to bond. I guess I'd come for the week if you have time for it, and would come to the 3-day if you can fit that but not the other?

In any case, don't delay your application while considering. You can always email in later with a changed timing preference.