I find the most important thing when they first arrive is warmth and electrolytes. Mine had a fairly bad shipment and I managed to revive a few that looked all but dead (stiffened, not moving, on their sides and stretched out). I had them sandwiched between a pet heating pad (gentle direct warmth) and fed them electrolytes until they perked up again. When they were alert enough, I began feeding them mash.
I’ve been mostly brooding quails most of last year, so I haven't had chicks for a while. I was pleasantly surprised at how easy it is to “force feed” them. Just open the beak and pop some mash in the back, they will swallow it themselves.
Thanks to this I’ve managed to keep a few alive that weren’t eating much/anything on their own. Unfortunately the extremely weak ones passed during the first and second nights, sometimes the shipping damage is too much
So about 3-4 days in and I was confident the remaining ones were all going to make it. They’re now all happy and healthy 2.5 week olds.
That said, unlike the cheaper hatcheries my pet chicken is verrrrry good with shipping and more likely than not, you’ll have an excellent experience with them!