This is a very interesting piece, and I generally enjoyed it. I'm not sure what to say because I don't think I've heard anything quite like this, especially with the color you get from the flute. Maybe slightly Messiaen influenced? It didn't really have any melody you'd be able to sing back to anyone, but that isn't necessary in a piece of music at all. If you can get a recording of the performance in December, I'd love to hear it. This would be very challenging to perform as a group, so you must have some really talented musicians working with you.
Overall, I thought it was a good listen. For the 4 note cello chords, are you having him roll them from the bottom up? I'm assuming thats what you wanted, and I think that'll make that section of the music sound much better than this (very good sounding, actually) midi realization.
Keep it up.