A couple of ways to approach the two audiences:
1. Generalize material where we’re not speaking directly to workers or to management, just to the reader.  I’m not sure this would work as well when trying to reach those in the work force as well as it would for managers.
2. Write it as two books.  Even though it would be one book, we could write it as one part for managers and one part for workers, and encourage them to read all of it to get a better understanding of what each needs, does, wants, etc. Have you ever seen a double issue magazine that has a cover on the front and a different one on the back, and the back half of the magazine is upside down from the front half?  Could that work as a book?
3.Just write it from our experiences as employees and managers.  If we speak in the first person, then the people we’re talking to are the audience no matter who’s reading it.  The problem with this is, we’d have to convince them that we’re some sort of experts.

A topic that should really be hit on is the option to get an associates degree, then get in the work force with all of the general requirements for a bachelor’s out of the way.  Once the employee is in the work force, they can take advantage of their employer’s tuition assistance programs to help them get their bachelor’s degree.  I’m 29 and don’t know what I want to do with my life…people that are 18 are pigeon-holing themselves into a career that they may want to change before they even get started.

-Mike