Help need advise

MY husband's parents are really wanting our 5 year old to spend the weekend with them and have asked for months, I love his mom to death but his dad is an alcoholic has been for years, every time they visit he's drunk and acts a fool is mouthy sometimes starts arguments and cuses in front of my daughter who then slips and cuses to I do not trust him at all. I obviously do not want my child to stay overnight in that kind of environment, I have been putting it off with every excuse in the book, I've asked my husband to talk to them about it but he doesn't want to hurt his mom as do I, I simply cannot let my child stay there I'm terrified! She wants to stay with them to, how do I explain to them and my daughter that it's not going to happen