Reports arising from math workshops
From my point of view (as someone whose eyes are still tired after reading 180 application packets...), having this on your CV would not be a negative thing.  It should of course be on a separate list from your peer reviewed journal publications along with other technical reports, conference proceedings papers, etc.  

The positive aspect of this is that it shows that you worked collaboratively with other people at the workshop.  This is a particularly valuable thing for an applied mathematics faculty member, since our department (and our dean and VP for research) want to see faculty in applied mathematics who collaborate with other mathematicians and more importantly collaborate with scientists and engineers on inter- (or trans-) disciplinary research.  

In short, don't try to avoid being listed as a coauthor, do list this on your CV in a section separate from your peer reviewed journal articles and don't worry about it hurting your chances of getting a job.