I am so sorry about your cat dying @FriendlyMedusa, we had to have our dear dog put to sleep over 3 years ago, and I still miss him so much. I am also very sorry to hear about your broken fingers, that must have been terrifying as well as being very painful 🥺 Have the police been able to arrest anyone yet?
My dear dad was made redundant when I was a child, it was from a very large private company that worked in the air defence and travel industry. The company was the main employer in our area, and my DDad was in a middle management position before he was made redundant. However, what made the situation so bad for my dad's mental health, was that he was the only one made redundant. It seems that for whatever reason, his face no longer fitted within the organisation. Unfortunately, it took him about 6 months to secure a similar position, which was with a similar company, in a neighbouring town. So, although it was many, many, years ago, I think that I do understand the stress your family is going through, well at least to a certain extent.
So what I am going to ask you now O.P. is just me trying to find out if there is a less 'nuclear' option for you and your husband to consider at this very vunerable time in both of your relationships with his parents. My first thought regarding your husband's parents, is that as they appeared to quickly change their tack from asking to stay with you for a few days, to requesting that you both meet them for a couple of hours, is that they have - of course, and quite rightly - discussed your DH's redundancy, and your family's awful month, between themselves, and that they had maybe come up with an idea, probably far too quickly, that they think is a brilliant solution (of which I am not going to hazard a guess) for both of you, regarding your husband's very recent redundancy. In doing so, their possible excitement about this 'solution' may have led them to feeling that they just had to share it with you as soon as possible, and that you both refusing to do so until next month, just threw them, and as I mentioned before, led them to both clumsily, and outrageously, send you that horrifying message?
Did you and your husband give your In-Laws all the same details that you gave us in your OP? If so, do you think that their over eagerness to help, might have led them to come up with 'that' potential proposition for you both - hence wanting to be able to see you both for at least a couple of hours - so that they can put their suggestion to you in a face to face 'get together'? As an in-law myself, I am scrabbling quite determinedly, to find a way for both you, and your DH's parents, to meet up in a calm, and hopefully reasonably friendly, manner! Good luck @FriendlyMedusa with however you and your husband decide to deal with this situation 🤞🙏💐