Try using the following RAM:

• R = Responsible
• A = Accountable
• S = Support
• C = Consulted
• I = Informed
• O = Observing

It's the last one "O" that I draw your attention to.  In your meeting agenda you assign "O" to the developers and designers.  They are invied to the workshop but as observers only.  This keeps them in the loop while freeing up the meeding for a true needs assessment.  This must be socialized with the stakeholders, the team, the PM and the sponsor.

Perry

 We have a list of models for RML that is pretty comprehensive from a requirements point of view. We organize the models into people, systems and data models. People models organize information from a user point of view. System models organize information about the ecosystem and individual systems. Data models organize the flow of data through the system and individual data elements (from a business not technical point of view).

http://www.seilevel.com/wp-content/uploads/RML-Language-for-Modeling-Software-Requirements1.pdf

Here are some articles on how to prep sessions. If you search the seilevel blog you will probably find more.

http://requirements.seilevel.com/blog/2008/07/how-to-prepare-for-requirements-sessions-with-your-users-tip-1.html

http://requirements.seilevel.com/blog/2006/04/jad-sessions-part-1-the-need.html

http://preview2.seilevel.com/2006/04/jad-sessions-part-2-roles/