What are the better decisions that he is making? It sounds to me that he is attempting (again) to manipulate you, so that you decide to send the money.
I would say this. Send him the money for you, if you want. Without buying into the idea that he is any different. These are magic words. No more, in my opinion.
This is my experience, too.
It is hard, but I think he needs to figure this out. That's one way to look at it. There are soup kitchens. There are free programs like Salvation Army. There are all kinds of jobs. Maybe if he has to look in the mirror, that reflects back the truth, he will decide to make steps to change.
The other way to look at it, is your way; that he has paid you back a couple of times before. And might again. Without the expectation that anything will come of it.
They made the decision to leave their jobs. They could have worked until they had sufficient money to make this trip and to handle the contingencies. Apparently, they chose not to. To me, sending money is like giving them a prize to have thoughtlessly indulged themselves. They don't want to accept the consequences of impulsivity. None of us do. But that is the price we pay.
Where does the learning come from if we bail them out?
But that said. All of us have done it. If you need to do it, join the club.
