Recip content question - what if content is moved from one site to another?

[uhwebs]

I currently have a site on a topic, but I'm starting a new one on a very similar topic (ie, instead of "widgets", it will be "widgets for kids"...)

Is there any harm if I take articles off the current site (delete them) and move them to the new site? Or vice versa (I publish an article on new site, it doesn't work well, move it to old site)...

Not sure if this would be duplicate content or not... another option would be to slightly re-write articles from one site to the other (though I'd only do this rarely for topics that need to be "explained" simpler). Is this OK too?