An hour and half sounds like enough time to workshop 3-4 songs, if some need tweaking and only 1 or 2 are in need of a complete re-think, latter which may or may not be completed during the workshop.

Here's what I'd love to experience attending such a workshop:
Just a few songs to show the principles. Maybe you pick them by design ahead of time, or by lottery, having everyone drop their name in a hat on their way who wants their song workshopped. The former gives you a better chance to ensure a variety of issues are addressed.

Then have a go at working them up, with the whole panel contributing to a final version. Every idea used may not be to the songwriter's liking, but it's about teaching the whole group too. Writers sometimes get in a rut and need to be pushed into trying uncomfortably new things.

I definitely want to hear before and after, and I want to see what is tried and discarded on the path from hither to yon. I want to see addressed (not an exhaustive list, just a few things that come to mind):

Ways to improve on
..Too many stories or pictures packed into one stanza or song.
..Rhythm of music fights rhythm of lyrics with unpleasant result.
..Too-disconnected ideas within lines or stanzas.
..Chorus clashes with verses (music or lyrics).
..Wanting more emotion in the lyrics.
..Rangy melody.
..Chords don't follow/fit melody.
..Accidental plagiarism.

Tips, tricks, tools:
..How to use contrasts to heighted impact e.g. quiet music with violent lyrics as inThe Band Played Waltzing Matilda).
..major vs minor key.
..you tell me!!

I won't mind that my song wasn't chosen if I can follow the application of ideas or principles to a variety of problems.

You should know, however, that I won't actually be attending that particular workshop.