I can tell you that if you start taking your dogs on fun trips on a regular basis they will start to enjoy the car. If you only take them to the vet or to the groomers then they will associate the car with something unpleasant.
Take fun trips a couple of times a week and see if that starts to get them a bit more excited about travel. If they are used to being home all the time it may be difficult to change their mind set about going places.
How do you bathe them and with what? Is there anyway you can make it easier on them? Gracie hated baths at first but she has accepted the fact that she is getting a weekly bath. I do it in the kitchen sink. I put a special mat in the sink so her feet are stable and she feels secure. I also purchased a sprayer from PetCo:
Rinse Ace 3-Way Pet Faucet Sprayer at PETCO
It has cut the amount of time I spend with her in the sink in half and I am better able to be sure I get all the soap and conditioner out of her fur. It has 3 spray speeds. Using a conditioner and also a spray conditioner makes comb out time easier and quicker also. As soon as she is combed out I blow her dry with the hair dryer. The easier you can make it for them the better they will accept it.