OK, well ignore my last very complex response.
You could do this manually by adding rows into the necessary tables and adding cms code references to the corresponding rows. This would take a pretty good understanding of everything that is going on, but is certainly possible.
A second option is to buy a single license of the full version of powerCMS for you. This would allow you to update the database through the powercms admin and add content areas. You could run it on your localhost and add the content you need and then use the limited powerCMS version on the live site to prevent licensing problems...
The third option of course is to get powerCMS for each live site, then you don't have to worry about running it locally and having to import and export your local database to the live site to make changes. This is the easiest, but has a per-site cost associated.
This would make it relatively easy to update the links created with menu writer to be editable with the cms.