Not so extreme, I moved my own cats across town. I found that I fell into a catch 22...much like my clients.
Leaving them at the current home was stressful for them and me. They were scared of all of the boxes and strangers in the house that were there to help pack. At first, the boxes everywhere were fun right? Lots to explore. But then the cats were in the boxes and needed to be moved. Not to mention all the strangers in the house! One cat loved new people and saw it as an opportunity for extra people to pet them. The other was scared to death and would not stop hiding. One of them was fascinated by all the activity and the people going in and out. Could they go outside and explore? They were under foot and in danger.
Moving them to the new place ahead of the furniture and their family was just as problematic. They would be there alone....in a new place...without their "people". But it was also an opportunity to check it out. Find the sunshine. Find a good hiding place. Have some quiet before the bustle of all the boxes coming into the new space. One of my cats found such a good hiding place, that I still to this day don't know where he was for the first couple of days after we moved in. I knew he was eating at night but I didn't see him at all until the 3rd day when it was just me in the condo and he jumped on my lap unexpectedly.
From your pet's point of view, there is a lot of change happening all at once. There are calming sprays and other medications that can be prescribed by your pet's doctor to assist with the move. I have found that making sure that they have their things with their smell in a quiet place makes all the difference. And just having each other.
What are your tips for moving day or the weeks ahead of the actual move? I would love to hear your suggestions!