Happy to report our girls seemed to do just fine having spent the better part of two days all alone.
As soon as we got home from the airport last night at 10pm, I grabbed the flashlight ("electric torch" to you UK folks) and went outside to make sure all was fine.
In the dark, my initial scan of the eglu and run showed that no one had broken out (or broken in), and there was still a respectable amount of food and water left in the bowls. I quickly shined the light inside the eglu, and there they were: our two chooks asleep side-by-side in the nesting box.
That's a habit I'll have to break them of sooner than later (via putting a ball in the box to crowd them out), but for now, I'm happy to see all is well in our little chicken-land.
When I went down to feed/water them this morning, I could see they'd spent the better part of their day(s) trying to dig out from under the run. Thanks to Omlet's intelligent design of the run (specifically: the six-inch extenders off the edges), the girls didn't even get close to digging out. I am going to have to reduce the amount of mulch under their run, though (currently: six inches deep) so as to thwart any other attempts.
While I didn't see a noticeable jump in the girls' overall size since I last saw them Saturday morning, I did notice that their combs and faces are now a bright pink. No sign of wattles sprouting yet, but I'm sure that's just around the corner.
Another thing I noticed when I gave them fresh water: they gulped it down as though they'd been waiting for it. Here I thought all I needed do was make sure there was water in the bowl, but it seems they really do want fresh stuff more than just wet stuff. I'll make sure our chook sitters know this next time we go away.