Sun almost certainly. If they are bearded iris, rhizomes, they may be fine in that ditch. I have mine planted on a slope, it helps keep their roots dry. Bearded iris don't like wet feet. Two weeks out of the ground is nothing for bearded iris, so don't worry about that. If they are Siberians, which are more rootlike, then they like more wet soil. There are other varieties of iris out there, but these are the ones most common around here.

I just stalked my Sister In Law on Instagram :) I found pics of her Irises from when she posted about them May 2016. At that time she said "1st year they sleep, 2nd year they creep, 3rd year they leap - good thing I divided them last year"

and posted lots of pics of them in bloom. They appear to be what I think of as "garden variety" iris. Big, tall, showy purple blooms with darker beards (or the part that hangs down, I always assumed it was the beard part of bearded iris when they were big and full like that)... I know that's not a lot for a formal ID.

Where I'm planting the ditch lilies (I had them there for 2 years, then had to dig them up for construction, they're just going back) is dappled sun at best, it's between a few trees and the street, and it's truly on the side of a ditch where they may potentially have wet feet.

Yeah, those are bearded iris & prefer full sun, although older
varieties can handle dappled shade fine. Wet feet is a big no-no though.

Hmm - I have lots of spots with full sun, but a spot where I want to plant AND where I can actually get my hose to reach is another question...

Should I cut them down to a shorter size before replanting? She just dug them up and threw them in a bag, full leaves and some old flower stalks and all...

Yes, cut them back to 6 to 8" tall, plant with the top of the rhizome showing above the soil. You can water them in when you plant, but unless you have an extended dry spell, don't worry about watering them. Less is more for iris.