We moved them outside this morning, and they didn't blink. For chicks that had never seen outside, they didn't seem fazed at all. It seemed cold and breezy to me, but they didn't act any differently, so I think they were comfortable.
We had only assembled one Eglu so far as we assumed they might benefit from group body heat while sleeping, but we decided to assemble the second one while they hung out in the first one and finished just before sunset. We went to put them in the cubes (I crawled around inside catching them and popping them in the coop while my husband opened and shut the coop door), and that's when we discovered that some of the clips on the run had popped off, so chicks started escaping. That was fun. We finally caught everyone (shout-out to the cat for NOT eating any) and got 12 tucked into each cube. They love the cubes and went to sleep as soon as we put them in.
They have tons of room in the cubes/runs right now, so I think they'll be okay until the age when we can return the roosters and unload the extra hens. And believe me, I do not want a feather more than what fit properly in the Eglus, and I am not buying or assembling anything else, so we will definitely be unloading. It would be simplest if we just had a ton of roosters since the hatchery will take those back, but my husband has coworkers who would take hens, so we're set either way.
Thanks again to everyone--so very helpful!