Beautiful set up you have there! Lucky girls!
I'm a low-tech kinda guy, and my laziness is reflected in my chicken run. I have a 16' x 20' foot open yard for the birds. There is a 3' x 6' "loafing shed" in one corner to give them shade in the summer and shelter from sudden thunderstorms the rest of the year. The yard is dirt...period. I throw them scratch every morning, and what weeds/garden scraps that are seasonably available. I also give them kitchen scraps, collected in the "chicken bucket" on by the kitchen sink.
They happily scratch, root and cultivate that plot of dirt to their heart's content, rejoicing at whatever insects or worms get in the way.
Yeah, it's a chicken yard, complete with poop, holes they've dug and scraps (weed stalks) they have declined. Every 18 to 24 months I roll the rototiller into their yard and turn it over properly. I may skim some of the beautiful topsoil off for a flower bed, or planting box. Then I turn them back out into the yard and there is mad scramble for any creepy-crawlies I may have unearthed. Their favorite holiday!
So my advice to any folks stressing over a well manicured chicken run is: don't use any litter and just let 'em be chickens.