There are so many variables in your scenario that nobody can give you any sort of definitive answer. Only thing we can give you is based on conjecture. Anyways, as for when you can cancel, see this is kind of a floating date. We don't know, because Apple as others have noted, tends to underpromise and over-deliver. So in theory, you could still get release day delivery. In which case, cancellation date would probably be in the next couple of days. Now if delivery is closer to the 17th, then I'd say you have till probably early November to cancel without there being any issues.
Now as for your friend and the hotel, I wouldn't have done what you did, because he's only there the 12th-15th. The phone could be earlier or later. Too much is unknown. I wouldn't have risked it personally.
Best of luck to you. I hope it all goes well!
And yes, we're ALL hoping we get it sooner other than later!