Update 6 - 39% funded + found cheaper flights
With the help of Google flights we've found some cheaper flights*, thanks for the tip @tkimnguyen.
With this new information we've adjusted our target further downwards (still working with the assumption that we purchase our tickets this week). With the adjustments and recent backers @pbauer, @esteele and @ebrehault we're now 39% there.
Thanks to all those who have helped to fund this so far. At 39% funded we're seeing enough "daylight" to go ahead and purchase our plane tickets this week.
... * tip: I've found Sunday to Monday airfare cheaper than Saturday to Sunday airfare and, in general, weekday travel is cheaper than weekend travel.