Why does everything have to be made so difficult? You don’t want to go, don’t go. Tell her you already have plans (don’t elaborate – your plans could be for taking a walk, or eating cereal).If she persists, asking for a future date, just tell her you never know how you will be feeling, so you don’t plan in advance.
As to the issue of her children’s behavior – it is totally UNACCEPTABLE for parents to remain passive as their children wreck someone else’s house (I won’t even DISCUSS the knives). If they are that laid-back, then invite them without the children and when they expectedly say they can’t come without them, say that you are concerned that their children will hurt themselves or inadvertenly break something, because they don’t yet have the patience to sit still, and you are too tired to watch them yourself. I think it is time for parents to get the direct message that if their kids are not going to be behaved (as many are not capable of being at a certain age)or alternatively, be supervised by a thoughtful parent (and it is the PARENT’S fault if they are not), they will not be invited out too often. End of story.
And by the way, in a gutteh shaah when your own child is born B”EH, please do not be that parent yourself of whom you complain, who thinks everything her child does is precious, even as she is tearing up someone’s living room. We tend to see such faults in others but not in ourselves (not saying you will, but just a cautionary thought to you).
Note to all parents who fit this description: People might be too polite to tell you that your children are behaving like brats and that you are behaving equally badly because you are allowing it to happen. Grow up. No one enjoys children who run wild and are out of control. It is not pretty, it is not adorable, and it is potentially dangerous for them, because limits are not being set properly on their actions and they are not learning about acceptable and uncacceptable behavior. I had visiting (frum)grandchildren from my neighbor, running wildly and screaming like banshees through my property, hitting my retaining wall with a bat, which is across the street from them), while my children and baby ainekel who were visitng for Shabbos, were trying to take a nap in the afternoon. Twice we had to go out to shoo them away. Where were the parents? NOWHERE in sight. And these were kids of all ages, including very young toddlers, who should not have been across the street to begin with.
Sorry for my soapbox. This is an issue with me. I don’t get angered easily, but failing to properly take care of children and instill middos in them IS my personal hot-button gear grinder.