You know, your best bet in dealing with kids with bad manners is just to try to ignore them as much as possible. Through the years, I have tried various tactics, but have came to the conclusion, that if they aren't brought up with general manners, there is really nothing you can do to correct it in one evening.

With that being said, I would not let them walk all over you or destroy your house. Tell they to "stop" if they are playing with untouchables, etc... and to quiet down if they are too loud. If they are continually complaining about the food, I would just tell them they don't have to eat anything and dismiss them to another room. Is there a chance you could have a tv on in a room for them to be able to watch? It may keep them entertained enough.

Don't sweat it too much. If I recall when most people make posts like these, their fears tend to be worse than what actually ends up happening.

And, if you have the alchohol yourself, you should be sharing it; but there's nothing really wrong with being out of brandy for the night!

No reason in the world why you should tolerate bad behavior by the kids from a previous marriage ( or not a marriage) of a girlfriend of your brother in law. Say...'I am sorry, that is not allowed in here...and tell your husband "Honey? Will you see to this?"
You are a hostess, not a door mat....you have the obligation to smile, serve them lovely food....but not to let anyone dominate and be rude so that others are uncomfortable as well.
I have a personal story....
About 22 years ago....there was a Christmas guest in my home who was rude, overbearing and rude. He made fun of my nicely set table and our lovely meal, came to the table dressed in a T-shirt, jeans and other strange accessories. He made everyone else in the family uncomfortable, to the point where one of my 20 ish children cried and said "he spoiled Christmas"....so I said" youa re not welcome to come for Christmas next year"....and a few years after that we met at another family affair and he proceeded to knock on my hotel room door and pick an arguement.....
I don't see him any more....he's my brother. But the happiness of the rest of the family is more important to me that any relationship with him.
You have an obligation to the rest of your guests....don't let a few spoil a good thing.
Linda C