Sully, what I find confusing is why your college would be arranging a 'holiday' to New York in the first place! Is this some sort of study trip being arranged by them in connection with your course? I've never arranged a holiday for my students in my life - I have arranged a number of study/field trips and my prime consideration has always been to keep costs down. And this is why we've sometimes done the equivalent of a DIY and booked travel and accommodation separately etc. We've even used hostels sometimes for the same reason :-)
If it is a study trip, offered as part of your course, they're not necessarily required to have an ATOL licence though it would be worth asking about bonding/insurance arrangements etc if things go pearshaped. In my experience, colleges and and universities take their 'duty of care' very seriously with regards to study trips etc because legally they have far greater obligations to you than any TO or TA would have towards you as a holidaymaker. Your tutors will have had to carry out a full risk assessment etc before getting the OK from their institution to go ahead with this sort of trip.
I am assuming that your college is in Manchester and I would be very surprised if your college was expecting you to make your own way to Gatwick. It would be usual to arrange group travel to the departure airport - mainly so that one can be sure that everybody is there in time for check-in. So, yes, you'll have to leave home earlier than you perhaps planned but do you know why the departure airport was changed? It could be that this is the responsibility of the airline or company the college booked the flights through - even TOs do this as many threads on this forum will testify to. Also, do you know why the hotel booking was changed? Again this could have been done for a number of reasons and might be outwith the control of the college. Compared to some of the horror stories you'll see on this site the changes they are proposing aren't that great.
I would never make any sort of booking for a field trip without ensuring that the students took out appropriate travel insurance either via a group policy sorted out by me or them providing me with proof that one they had taken out themselves provided comparable cover. For that matter I'd never book a private holiday without decent insurance and I'm assuming that you have got insurance too. So you might want to explore what your options are with regard to whether you'll be covered for any cancellation you want to make.
Finally, it's only fair to say that I have now stopped arranging group study trips abroad because they're not worth the hassle. Students these days not only tend to treat them as holidays but expect to be able to behave as they frequently do on holiday. This also meant that it became harder and harder to find reasonable budget hotels that would actually acccept a booking for a student group. More importantly I eventually had my fill of being responsible for students who got drunk and took risks with their own personal safety. The legal 'duty of care' meant that if harm came to them I could be held legally responsible - a young woman from a neighbouring university got attacked whilst returning alone in the early hours of the morning to the hostel she was staying in after a night out and sued the university for not warning her that this was a dangerous thing to do and that they had failed in their 'duty of care' towards her! So I have a great deal of admiration for tutors and teachers in this litigious age who still do arrange study trips etc despite all this.
I am still willing to assist individual students who wish to spend time working or studying abroad by finding them a suitable placement contact etc, usually through another partner university or college, but leave them to sort out their own travel and accommodation etc on the grounds that if they can't do this for themselves then they shouldn't even be thinking about going in the first place :-) Fewer and fewer students are prepared to take on this responsibility and also be responsible for sorting out the financial side as well hence why it is at least 3 years since I even did this.
SM