Firstly (I'm really sorry about this) but posts with swears blanked out (like your title) REALLY annoy me. There are LOTS of words out there. If you don't want to make a swear, use some of them. If you're going to swear (spoiler... we all know the word you were thinking) then just do it. It's allowed... we're all grown ups!
bitching, people. She was saying BITCHING!!!- (sorry, I know that's unhelpful!)
Ok. So.. It's absolutely HORRID of people to slag you off in your own house. This happened to me in March. I was LIVID.. I'd cleaned the whole fucking place, put clean bedding on their and their DC's beds, brought lovely food and treats and then listened to them moan about me. I wanted to ask them to leave! (but I also knew they weren't knowingly be malicious).
It's LOVELY your DH stepped up. Most posts on here on this kind of theme don't have that support, so bonus points to him.
Agree with a PP who says send them out tomorrow without you.
Also agree with most PPs who point out a 4 yr old is very different to a 2 yr old and frequently finds sharing very difficult. I like the idea of getting your 4 yr old to help put some toys "out" and some "away"
Buuuuuut there's a teeny-tiny corner of me which is kind-of thinking... do you need to look at what they're saying and examine if there's any truth in there? I'd ask your DH, because he seems quite switched on.j
The relationship between your DC and your SIL's should be lovely and encouraged. Family is important, I think. So that means supporting the good bits, encouraging others to minimise the bad bits. Deciding what to ignore.
Try and be the grown up here!