This is all very frustrating. You had plenty of opportunities to firmly and clearly state, "No, this is not happening."
I got the message about hosting through DH and at the time it was mentioned I said do you realise I'll be 9months, we've just got over a cold and I don't want to get sick again especially not with covid season on the rise, and the baby could come at anytime plus ....... etc.
No, DH, we will not be a hosting a party in our house when I am 9 months pregnant. It's not appropriate. (Not all this long winded wishy washy explanation. A simple NO. It's not happening. End of)
So anyway my IL finally messaged me directly and asked if I was aware of the plans, I said it was mentioned
At which point you should have told IL "No, this will not be happening because I will be 9 months pregnant at the time. It's not possible"
There is so much about the party that was unknown like time start and finish times, exactly how many people are expected. I asked about all of that and if invites had been sent out - the answer I got was basically yes invites were out (I am yet to see it) and that final numbers would be confirmed next week but it's now looking like it could be 30 adults and 10 children. I said I'm not going to be around for it because I'm not comfortable with it, I said I had no plans to entertain after DH birthday as that was taxing enough and I'm just too tired at this stage of the pregnancy to host people and the risk of catching something is high as my immune system is already low. The response was "ok in understand". Not ok we'll move it or cancel
At which point, if this had still happened after the early 2 firm "No"s.
"You must have misunderstand. The party cannot take place at our home. I already made that very clear. You will need to find another venue"
she's disappointed that no one seems to have sense enough to stop this from happening or no one is better advising IL
I'm sorry OP. But it was up to you to stop it. Not a random "somebody else should stop it"
Gosh I feel so sorry for myself and highly annoyed. I can get very disrespectful if needed but I really don't want to go down that road and as newlyweds I'm trying to respect his family even though it's clearly not being reciprocated. Hopefully there won't be a next time because my attitude will be complely different should such a request be mentioned. And hopefully me staying upstairs will be a clear enough message!
There will be a next time OP - because you have shown them that you will allow your wants and needs to be steam-rollered over. You need to learn to say NO, loudly and clearly and straightaway, nipping any nonsense in the bud.
And I'd be having words with DH too because he needs to learn to stand up to his family too.