I can't help you for your trip but let me give you a tip for trips in the future, because I've had the same thing on organizing ski trips. At the time of planning you will get a lot of people who say they will go and that it sounds exciting. When it comes time for booking or getting solid committment from them, they back out and flake on you, because they haven't given you a dime.
You need to get money from them at the very beginning before you book a single room, flight or event, and tell them it is money that they won't get back if they choose to change their minds. There will always be some friends who you can depend upon, but most others will flake unless they stand to lose a fair amount of money.