Hey Julie,
yep, looks like you're on the right track, just know that that old hay is going to attract mice too. I definately think you should leave it there anyway, use it for it's insulation value for now!!!! Mice will just tunnel in the bales and make little homes, but that's just the way it goes. Just be prepared for it!
I did much the same thing one cold winter, on one side of my coop that I couldn't do anything about in the winter, (steep drop off and too awkward to work on in winter) and the mice got evicted come spring, with hens chasing them gleefully!!! Not many (actually I didn't see any) got cought, but the hens had a BLAST trying. The bales got wheeled out to a corner of the property, got busted up, and composted seperately from the regular compost. It was quite usable, but I wasn't sure at the time if there would be too many weed seeds etc, so I kept it seperate.
Your chickens will manage, all we can do is live and learn. Thanks for sharing BTW, we all benefit from each others' problems and solutions!
PG