I think depending on what your dogs are like in a car, you should take them with you. Seems they have experienced some trauma in their travels? Depending on your car, why don't you rather buy a Travall Cargo Barrier for your dogs? It will keep them at the rear of the car while you or hubby can concentrate on driving to your destination without too much hassle? http://www.travall.com.au/dog-guard.
And, it sounds like it would a FAR cheaper option than $4000!! That's just crazy.
Good luck!!