Thanks, wysiwyg, that'd be great. I guess the secret will be to prepare for any enevtuality. I may ask everyone - supposing there're not too many - to play a verse of their best party piece, and take it from there.

Actually, before that, I'll need to establish who can play a couple of basic chords, who has sung/played in public, where they hope to go with it.

I sort of think about taking a simple "two-chord" song, and seeing how to make it sound good at that level, and then looking at how to take it a step beyond by putting in some simple inversions and/or substitutions.

Hey - why am I panicking? I've got at least three weeks to prepare. AAAARRRGGHHH!!!! ;^)