chosenone,
Your dad is an alcoholic of many years standing and you know the 3cs (you did not cause this, you cannot control this, you cannot cure this) to be true.
Re your comment:-
"Yes i, unfortunately know about the three c's thanks to other addicts in my family. I can not being doing with another"
Sorry to write this but you already are. Alcoholism as well is truly a family disease, one that does not just affect the alcoholic. You're all affected by his alcoholism to varying degrees. Your mother for instance plays out the roles of codependent, enabler and provoker (she never forgets). She remains with her H for her own reasons.
Why does your DH to be find it funny that your dad has a serious drink problem?. What have you done already re taking him to task over this?. He's doing his own bit (as is your mother) to enable him isn't he?.
Unfortunately the only one who can address your dad's drinking problem is your dad himself and he shows no sign of doing that. He may never do so either, that is a real possibility here. He could go onto lose everything and everyone around him and still choose to drink afterwards.
Your wedding day will give him the ideal opportunity to drink; his primary relationship is with drink and his next thoughts centre on where the next drink is going to come from.
It may sound like a bridge too far now but I would seriously consider whether you want him there at all. Where are the consequences for his actions?. You run a real risk of him ruining your special day due to his own drunkenness.
You can only help yourself ultimately and talking to Al-anon would be a good start. Attending their meetings would also be good for you, at the very least you need to read your literature.