Using my established sites to promote a new project

I have four PR3 sites and two PR2 sites that are old, long-established Internet sites and have good, mostly U.S.-based traffic. They are mostly of non-commercial nature, although they do have some minimal AdSense income.

My new project is an article submission directory. It is getting excellent traffic from all over the world (especially India, but also some from Western countries). The Alexa rank is excellent (less than 80,000), but the PR is zero, probably because of crappy submissions. My monetization strategy is to sell "featured" links that will always stay on the front page, and having good PR is crucial to making those sales.

If I place a "sponsored" do-follow link or a "Designed by" link to my new project in the footer of each of my old PR3 and PR2 sites, will that help the new site climb to PR1 or PR2, or is that not enough? Will Google penalize my other sites for linking to a site like that? The reputation of my old sites is important to me. I also thought about placing a concealed link (white text on white background or a one-pixel link), but Google has written a lot of warnings about that, so I am hesitant to do that until I hear from people with experience. Thanks.