Carbon bars definitely smooth out the small vibrations. I went for Easton EC70 and EC90s. Got good cheap deals on eBay.
Having done some carbon laminating (boat building) in the past I know that both flex and stiffness can be designed into carbon structures, dependent on what you need where. I assume you're looking a carbon rigid fork?
Regards multi day adventures you may find some useful tips by checking out a chap called Sean Conway. He does some crazy long distance stuff.
A link to his youtube: around the world cycle kit:
https://www.youtube.com/watch?v=JTMkhH7T5uY