Episcopal marriage-Drunken Rehearsal?

[Anilew]

I'm very torn on how to handle my son's marriage to an Episcopal girl. He was raised in church but is out at the moment. He is a successful businessman, and her family is wealthy. At her engagement party and later at her first wedding shower, both in Georgia, everyone was quite drunk. When we have the wedding in October, and we host the rehearsal dinner, we don't want to allow drinking. At their engagement party and wedding shower, it was their custom to make toasts and hold their wine glasses up. It caught us off guard, so we didn't hold our sodas up haha.
How can we be kind to them but not allow drinking at our rehearsal dinner. I'm afraid since they all drink so much, they will think we are being rude, legalistic, etc.
Tell me, do we just give a speech but without a toast. When we got married 35 years ago, no one said anything. We all just ate and laughed. I'm just so scared. I don't want to risk not getting them all saved. They are the most loving ppl to be so drunk all the time, and even my sons future bride says they are all alcoholics and she'd never quit drinking. It's a scary time as my son was in and out of jail for DUI over 6 years ago, but now that he makes &150k per year, he says "mom don't worry about me; I can handle alcohol now, because business has taught me to take a cab.
HELP! Tell me what to do so we stand for truth and also look classy like we know what to do.