Okay so looking at our group here. We have Lumrolur, Lorgim, Jack, and Aric (in not-spider form) who are Small size. We could send them up in groups of 2, which is 2 trips. If Aric stays as a spider, I guess he could probably just spider climb up the wall or something, right?
That leaves us with Oskar, Alma, Zeth and Russet (if he's medium, harengon can be either medium or small iirc), which is an additional 4 trips.
Now, Alma has some magic that could let her transform into a Small creature, so if Aric wants to stay a spider and climb up, she could double up with one of the Smallfolk and save us a trip.
But total trips we're looking at 5-6. That sound right?