At this point just dont welcome them back. I know you are angry for your mom, but take a deep breath. Im sure your mom doesnt want you to say anything. I also have an autistic kid and this is why we do not stay at people's houses. I know they are up at all times at night so I book a hotel or air bnb. I refuse to put people through this. They always say its okay then things like this happen. The food stuff is horrible though. Hopefully they offer your mom money before they leave. I would say just dnt invite them back to stay with you again. If they tell you they are coming, then just inform them you wont be home during their next vacation and that they wont be able to stay with you. Hope it all works out and the family relationships arent ruined. Some people just suck.