| Like Alice, I would advice caution , I don't think that you should prevent him but I do think he should have tried and tested means of getting through a hypo and be able to bail out without feeling that he has let either himself or the group down. With all the other kids around I doubt that he will get much rest.
When I was his age (long, long ago, and way pre diabetes) I did a similar fast for Oxfam. We were in the centre of London and supposed to spend the night 'safely' in a church hall. (thats what my parents believed, and probably today teachers would be far more vigilent). We actually spent most of the night in Piccadilly Circus, collecting money for our charity in various 'silly' ways. At the time I don't remember actually being hungry but we used a lot of energy up. When I got home I was absolutely exhausted .(Hence my caution).
After all those years I have great memories of that weekend. I'm glad I did it and think that your son should go but with clear safeguards in place. | 
