The background
Later this year, I'm hoping to move from a house to a first floor flat (apartment) with a balcony. I have two cats: litter mates, brother and sister, five and a half years old. They've been indoor cats all their lives. The new place is 30-40 minutes away by car. Location is the UK.
The breed is British Asian:
The Asian cat has an inquisitive outgoing nature.
It is intelligent and fun loving making it the ideal family pet. At the same time their gentleness appeals to elderly people looking for a loyal and devoted companion.
Asian cats are one of the few breeds which actually state in the breed standard they must be of good temperament.
Their personalities
I work from home, so they're used to having me around most of the time but are happy if I'm away for several hours, or if my partner has to look after them without me for a few days if/when I'm admitted to hospital. They are very confident cats on the whole. Vet visits are not an issue: I put their wire baskets open on the floor and they happily jump in and stay there if necessary for hours; they sing a duet all the way to the vets (25 minutes in the car) and then take over the vets consulting room -- no running and hiding but 'everything here is mine, including the new servant(s)'. (They've been described as the most confident cats the vet has ever seen).
However, I've tried boarding them in the past (in a shared run) at a trusted cattery nearby to get them used to the experience, but on both occasions we've had to terminate the process early (after two-three days) because they refused to eat at all. They haven't seemed to hold the boarding experience against me in the past.
My Question
How do I minimise the stress on them of the moving process? (I'll ask separately about how to minimise the stress of the overall change of environment, if necessary).
My options seem to be:
Board them in the same trusted cattery, starting from the day before the move and collecting them the day after the move. Concerns with this: they won't eat again and they'll perhaps learn to associate the cattery with a greater degree of disruption (we were taken from somewhere we knew and enjoyed, locked in a cage and starved, and then taken to a totally unfamiliar place with no birds in the garden for us to covet...). However, they will be spared the stress of the packing up/moving process.
On the day before the move, confine them in a room (probably a bathroom that's already been emptied, or the utility room where their cat tray already lives) with food and water, a cat tray and cat beds where the packing up process won't directly disturb them -- although they will still be aware of it going on. Brief the movers well, with visible warning signs. On the day of the move, take them in my car to the new place and again confine them to a bathroom that won't be opened until the move is complete. Concerns with this: they'll find being confined without human company stressful, especially if they can hear what's going on.
Have I missed an option or variant. And which approach should I take?
Note: I've read Keeping cat safe and comfortable while moving, but it may not be a duplicate because I have a secure place I can keep the Little Monsters at both ends of the move, and my cats cope well with their carriers and car journeys but not with boarding.