Your children are behaving as they do because they are being rewarded by grabbing your attention.
The first time a child does or says something be it sweet, funny or horrifying, they get attention from the adults or other children around them. To little ones, they don’t care about how others will react, and when others react, it is attention. As difficult as it is, especially in company, the last thing you feel like doing is to ignore the words or behavior they have learnt this from somewhere, perhaps another child and that child got a reaction. So they say or do something. If it is something lovely praise them not over the top, just a comment like …” Thank you for returning the book to the shelf” If the child threw the book, you ignore it, and get the child to focus on something else, then later say to the child, “I would really like it if you would place that book on the shelf please” When the child does this, then say thank you so much for helping mummy” No big reaction. If it is too soon after the book was thrown you can expect from the child, “no, don’t want to” Perhaps with a tantrum as there will become a battle of wills. As for swearing, they have heard those words, ignore it, then use a different word that might be new to them. Like if a child said “OH SHIT” you might, say “OH GOLLY GOGGLE GUMDROPS” some thing that has greater impact, and use this phrase in the situations that an “Oh shit” might be used. If anyone laughs or reacts crossly, you can expect the words to be repeated, regardless of what the word are! If ignored they are not getting a reaction so they will discontinue.
Sometimes as if a child pushes another child, just separate they children, provide something else to get their attention. If a child is hurt, the child needs attention, and that can be encouraged by the other child who caused the hurt. “Oh Please tell Sarah you did not mean for her to fall.” “Please tell her you are sorry” and move on. Sometimes one child means to hurt the other. That requires a different response. “Simon, that is unkind. Stop now!” More attention to to Sarah, not Simon! If needed, “Simon, I asked you nicely, now come and sit on the red cushion and stay there for one minute. You can come and play when you apologize can play nicely”

You need to find out where they are learning it from & put a stop to it!
Don’t yell at the children, they may feed off the attention.
Instead try explaining that it is a naughty word & throwing things is a naughty thing to do.
Get a box that can be hidden away & tell them this is the naughty box. When ever you say or do something naughty a toy or something they really like goes into the naughty box & they won’t get it back.
Stand your ground & be firm. Don’t cave.
You will build up a collection before the children realize your not playing & once the naughty behaviour has completely stopped over the next few weeks you can reintroduce the toys as rewards for good behaviour.
There is nothing more frustrating than a swearing child throwing things but these words can be picked up anywhere. My own sibling picked up swear words in a supermarket. It only takes hearing it once sometimes.
I wish you the best of luck.

It’s discusting that they have been taught this in the first place

cant belive you didn’t get any replies to this! im looking into the one, two three magic program for behaviour management. how did you go?

whoever is swearing infront of them needs to stop to start with or you will be flogging a dead horse, children learn from examples at this young age