hearthealth.....I like your idea of leaving it to your husband to be the one to deal with his family.
That takes you out of the middle. Then, if you don't want to go--tell your husband--and let him deal with it.
Not always, of course...but, family usually sides with family.
There is a good reason that alcoholism is called a family disease. It tears families apart.
I don't doubt that his family is covered with a thick blanket of denial about his drinking.
to me...it sounds like the writing is o n the wall, in regards to their relationship to you.
Perhaps, the best that you can do is to be minimally civil when you have to interface with them---for the sake of the children.
You are not alone, you know...there are millions of people who have acid indigestion whenever it comes to dealing with their inlaws...lol....