considering how much you now DEFEND your father,his drinking and the sanctity of these "trips" i'm wondering why you posted.
Unfortunately, he will. But I drive, not him. And that's on him. I do know for a fact he would take all responsibility, should something happen, so that I don't face anything. But again, I drive, so that helps. I know that's enabling, however, what am I, a 30 year old, going to tell my 74 year old father. "No! You can't do that!". I wish it were that simple, and I've tried. Falls on deaf ears.
you most certainly CAN tell any passenger of your vehicle or any vehicle you are IN that no alcohol is allowed. you are as you say a 30 year old grown up. what i am hearing is a ton of enabling and myth retelling. rather than stand up for yourself, you have built a legend around these trips where all your father does is drink all day, and you "tolerate" it in the name of a memory.
there are only four states that allow open containers in vehicles and based on your itinerary you won't be in any of them. so you are willfully violating the law. just sayin'..........
which is totally your choice. but this has a lot less to with his drinking, than the role you have made for yourself in the dysfunctional dynamics of an alcoholic family unit.