We've been running a one day workshop for several years now, inviting different folks from the area to come in. Some common elements:

Some discussion of what makes a good song, along the lines of posts above. I think this is best if it's a combination of your thoughts and thoughts of attendees.

Some discussion of inspiration; where songs come from, and how to get them to come. we've had lots of activity here, and it's usually lots of fun. people can work separately or in pairs or groups.

Participants bring and perform a completed song for the group, followed by discussion and suggestions. Have em bring a lyric sheet you can follow.

Participants bring an incomplete song, one in progress, to work on during the session, while you go round and work individually with folks. People appreciate the one-on-one time.

I don't think you need to feel like you've got the definitive answer on how it's done. If you can get a good supportive vibe going among participants, get em over the fear of sharing something personal like a song and inspire them to keep at it, I think you've done a great job. There are workshops that deal with "How to write a hit song" ie "Making it in the industry" stuff, which is fine, I guess, and then there's "Writing songs is great; period" type of workshopping. I guess you need to figure out what you want to do there. Lots of luck. sb