It sounds like you are quite the rock for your family. Sometimes that is quite the burden; I hope you have someone for YOUR rock, as well.
I hope, too, that you don't literally see it as "up to you" to get the family to stay together. No one can be that responsible for other people's behavior. But if you can help them do whatever they have to do, and let them know you are there for them, that is very important in its own right, regardless of whether they stay together or not.
It's so great that you have friends coming out to NY to help you move. What a wonderful tribute to your friend-making ability, and to their willingness to do so much for you! That is really true-friendship.