You know, I think I would go for option 1 too, especially if you can manage to keep some soil with them. They might even bloom for you. I don't think it would hurt them to take option 2 though. They probably won't actually root til the weather gets warm, but it won't hurt them. For that matter, option 3 will work if you have some bad weather & can't get them planted.
I'm lots of help, aren't I :) Iris are pretty forgiving. You might get some advice to pot them up, but personally, that is the one option I wouldn't bother to go with. I think they would be more likely to rot.
I hope they do great for you, whatever you choose. You got a great gift. What color are they? You will have to post pictures when they do bloom.

Well! Turns out they're not bearded; they're Siberian (equally welcome). A lovely big clump with a comfy chunk of soil. I brought them straight home and tucked them in without dividing.

Thanks so much for the thoughts - I'll let you know how they do!

I have divided and transplanted (rather rudely) Siberian iris a few times. Including in upstate NY 3 weeks ago. They are pretty hard to kill.

I've heard Siberians are particular about being moved, but I've moved them, like harryshoe, rather rudely & they barely blinked.

Having hoped for updates on other people's posts, I'd better give one on mine.

I divided the iris rudely - took a spade and chopped into 4 chunks! - in June or so, and popped each into a hole. They all thrived and have bloomed beautifully every year since. (Maybe they thrived a little too exuberantly, since I came back on the board wondering about giving them haircuts!)

Thanks again for the coaching, and best of luck to anyone who finds this in the future.