Implications of releasing news article on several websites

Hi folks. I'm dealing with a client matter that I could use some help with.

domainA.com and domainB.com (both 2+ year old domains) are putting on an event together, a new domain called domainC.com has been registered for the event (1 month old).

When a new piece of event information is announced, the same press article is released on domainA.com and domainB.com and domainC.com at the same time.

Furthermore, this same piece of content is picked up by other large news distributions and reposted again (they often rank in Google News, come up before the other domains, etc).

I assume this is indicating duplicate content, and could be penalizing the young domainC.com (plus other domains)

What is the best method to distribute these news articles? I am considering:

First posting the article on domainC.com

All 3 channels share / distribute this SAME link from domainC.com

A few hours later, post on domainA.com and domainB.com, with a link to domainC.com as the original source.

Thoughts?