The thing you need to ask yourself is whether you can accept his drug use. By the sounds of it he sees no problem with it, and doesn’t understand your concerns.
It also depends whether if you can accept it now, will it get worse, and will he waste more and more money on it, start staying out all night, sleeping all day, lie and cheat.
Mine got to the point where I believe he had psychosis because of his coke use, he was accusing me of cheating – and actually believed it, was staying out all night (and not seeing any issue with it) on random people’s sofas. Money was never an issue, because he earned well, but my life was basically like being a single parent, but also having to deal with his mood swings and rudeness constantly. I wont go back to that life, and hopefully now he’s seen the good life for the last 2.5 years, he’ll stay this way, he’s achieved so much more clean, and he can see the results himself, and speaks of coke users with negativity.
I would probably go on the holiday, but dont let yourself be fooled that this will be a new leaf, just enjoy it for what it is, and decide what to do when you come home xx