If you are committed to these trips no matter what then you will have to find a way to accept your father for exactly who he is and let go of the idea that he can or should be someone else. The amount or what he drinks doesn’t matter as much as you finding ways to detach from behavior you don’t like. Going on the trip limits your options for detachment, but continually struggling against something that isn’t going to change will just make you both miserable.

i wish you luck on the trip and hope that the memories you are creating together are positive.