Barbie,
I made a similar trip in my van from Washington state to Michigan with my two kitties.
They actually travel really well. But here is what I did. I bought an enclosure that kind
of looks like a quanset hut but made out of ripstop nylon and screen. It is large enough to
fit on the two seats behind the drivers seat. This hut is large enough to hold their two
carriers (which I left open so they could go in and out), a small travel litter box and a
small box of food and water. They could come out in their hut or go back inside their
carriers to sleep. It took me 5 days to make the trip, stopping at hotels at night, and
they made the trip just fine. Not even a meow!
Here is a link to the enclosure I have. It is the red one in the top row( mine is purple).
I swear by this thing. When my male Himalayan had serious surgery a year ago I was
able to confine him in this thing until he was well enough to let out. Take a look.
They make great products. Really well made.
http://sturdiproducts.com/
I hope this helps you.
Leslie