I wonder if you couldn't dig a few fans and just pot them up, keeping them outside, then move them to a good spot in your new gardens at your new home after you move, unpot them and plant. If the pots were big enough, then maybe they could make some good roots in the meantime and get started enough to make it through the winter outside. I think they really do need to be chilled for the winter to do well, so anything that included keeping them inside isn't a good idea. Or move your compost with some fans tucked in it, probably they will come up next spring! lol

Also, next summer ask if you couldn't have a few fans. It can't hurt to ask.

Mulch and plastic sound like a bad idea to me.

I'm with you on not counting on them being there with new owners. Since they are older beardeds they're probably tougher than some of the newer hybrids. I would do both 1 & 4. Many people have reported leaving a bag of rhizomes in an unheated basement or garage over the winter and having them do fine with spring planting.

I agree with Irisgal. Tall bearded irises don't need chilling, so if they are tall bearded ones that solves one problem. I would dig them as late as possible considering the weather (when and if your ground freezes is an issue) and dry them off really well, trim them up, and store them in burlap or paper bags in a cool dry place until spring.
Renee

What irisgal and hosenemesis say is true. I have had TB last through the winter in the dug up condition and then sprout in the spring, both in my unheated basement and in my unheated garage. Digging as late as possible is good advice. When I lived in Denver it didn't freeze too much for too long usually until quite late in the year. Hopefully you won't get a big early snow.