SpannerInTheWerks,
Don't take this the wrong way but i think you need to pick a couple of books up and start reading.
There is a lot of i "believes" and "seems" in your posts. Why not look at the aircraft document book, see who the insurers are and call them for a chat to discuss your exposure? I am sure they would be more than happy to cover the risk for you passengers and aircraft as a separate policy. You would be surprised how cheap it is!! Most clubs are very similar to what you have outlined.