Update: they got the nest back up the day before yesterday and my sister says theyre still up there and the parents are still feeding them. Cautiously optimistic; it looks like the rescue was a success.
Update, they made it through the rainstorm, my sister put them in an old litter container and put a rock in it to weigh it down an their parents are still feeding them—manically trying to find someone in the area with a step ladder currently.