Here's what has worked for me.  Cats don't like change (well, MY
cats didn't).  I would pack them up last, and put them into their
boxes just before the moving men start moving the stuff out. They
would be the firsr thing out of the old place and the first thing
in the new place.  Usually I have a good-sized closet in the new
place and I would put the litter box (with fresh litter) in the
closet at one end, small bowls with food and water at the other
end, put the box full of cat in the middle of the closet, then
open the door of the box and close the closet door.  If necessary,
tape a sign on the door -CATS INSIDE! DO NOT OPEN!

Then let the moving happen.  Get all moved in, pay the guys, go
out to dinner (or whatever you do), then when everything is quiet
again, open the closet door.  Don't touch the cat or try to drag
him out. Just let him explor on his own.

The first time I moved Fin, he sat in his litter box for 24 hours.
He didn't come out of the closet for THREE DAYS.  But after the
first exploration, he was fine, even though I was unpacking for
weeks.  The next time I moved, he was an old hand at it and
came out right away.  

Locking them in a bathroom is an option if you have more than
one.  I didn't.

Jane
- owned and operated by Princess Rita

I've found that just showing them where their litterbox is does the trick -
even if they don't use it just then.  I don't think you'd even need a scoop
of old litter for them to be able to follow their nose to it if they forget
where it is (cats' sense of smell is unbelievable).

If they're not used to the litterboxes being so far removed
from their normal area, then I'd say let them out by the
litter boxes, but leave any doors to the rest of the house
open (so they don't feel confined) and let them explore at
will.  Once they know where the litter boxes are, they'll
find them when they need them.  (Cats are pretty smart, that
way.)

We've moved house with Vino 4 times and each time I just let him out in
the middle of the floor and leave him to it for 1/2 an hour or so.  Then
I'll usually feed him some good food he likes, and then I carry him to
his litterbox and plop him in.  He usually doesn't go, but after that he
knows where to find it and always uses it right away.  He low walks for
a little bit but it's usually less than a day and he settles right in.
It's funny because he finds his favourite spots right away and continues
to use those same spots to hang around in for the whole time we live in
that house.
Good luck with your move!

No advice unfortunately, but lots of purrs and best wishes for
everything to go really well,
Polonca and Soncek