Hi:
You sound like you're going to be an amazing Yorkie owner. It sounds like you've already made up your mind about crate training, and I hope you won't mind if I just suggest you read the information here so you'll be fully informed about why many people do crate train:
http://www.shooterdog.com/alexfaq2.htm#PEE
The safest place for them to travel in a car is in a crate secured with a seat belt, and teaching them to nap in a crate makes that a cinch.