Mouse droppings & smell - would you say something?

Bit of background first..

The last time we visited the IL's it came up how they had a mouse in the house. Just the one, but he was very clean & they have never found any mess from it or smell. Laughed how it likes banana but only ever nibbled on one from the bunch..
Yuk but anyway...

Now we visited again today & normally I stick to either outside or the lounge area, it is well known the MIL is not the best at house keeping & lets face it they are well into their 60's BUT they have a 5 yr old foster son.
Now today we were outside all day pretty much. The kids were playing in the water & when DD went inside to change from her wet stuff she went into the middle room (bedroom smack in the middle of the house with no windows directly outside due to the veranda being turned into a sunroom) she called me to help her get her wet clothes off so I went in & was hit with an overwhelming stink of mouse. I actually said "Whoa is stinks in here!". DD then commented that yes it does & there is lots of poo on the floor. I glanced around & the carpet must be covered with mouse pee & there was a stack of mouse droppings all over the floor. Not just in corners here & there but literally scattered all over the floor! I made DD come out & get changed in the lounge room.
This room to the best of my knowledge is where the 5 yr old foster son can go play/watch TV etc. Its basically a "study" sort of set up I guess, books, old wardrobe with who knows what in it, TV etc.

Now we don't often go down to visit them because of MIL's poor house keeping. We don't eat unless its come out of a sealed packet & yeah its just gross. Day to day stuff at first glance its tidy etc but put it this way, there is still dog hair from the labrador that died almost a year ago still caught in the carpets etc.

Now, SIL is staying over for the week. She would have to be aware of the mouse thing. But would you mention something to her so she can talk to her parents about it? I think its possible that MIL & FIL don't even realise that those black bits are POO & the house is a damp musky smelling sort of place already so they may not notice the smell either so it is possible that while in the main living area this mouse is "clean", it clearly has mates & they are making a mess of the rest of the house. It concerns me not only for when my own kids visit (DS was laying out on that floor earlier looking at a book!) but they do have a young child in their care. I figure if SIL talks to them then MIL might not be as offended about her house keeping. I was going to pull MIL aside today & ask her if she realised but there were other visitors etc so I just left it alone (and scrubbed my hands!) then we left shortly after.

So yeah do you think I should bring it to SIL's attention (I don't think there would be much reason for her to go in there so she may not see it) or just leave it alone seems I don't live there.

I think I would have to say something, either to MIL or SIL. That is pretty gross and if they have foster kids, they may be in trouble if social workers come for a home visit.

As above. I guess you just have to use tact even when approaching SIL, so you can get her more on side than "she said this...." (in my best whiny voice). There is never just one mouse. Good luck.

I would go directly to MIL. If you are not comfortable doing that, perhaps your DH could speak to her?

I would definitely go to the MIL and tell her (and I'm a very non-confrontational person). She may not realize the droppings are there, and you'd just be stating a fact, not making any judgements. I'd appreciate someone telling me, if it were my house. And odd as it sounds, I have had the situation occur in my house, where droppings appeared overnight! It was in the spare room, and I went in one morning to find droppings all over the floor. I cleaned everything out, couldn't find any animals or entry-holes or anything! It was very strange. Haven't seen any animal poo in this house since then!

Could your DH offer to do some spring cleaning for them and spend a couple of days getting the place clean again, and put some ratsack down at the same time?

Nope, none of your business. Just don't go back there, ask to meet them in a park or restaurant in future.

Yeah I'd say something to MIL. Their health and the child's health is at risk with mouse droppings. If there wasn't a child involved I wouldn't press too hard, but because it's the child's play room I don't think I'd stay quiet about that.
It's just a matter of doing it tactfully.

DH is already very uncomfortable in his parents company & he learn his cleaning skills from his mother so... LOL. Besides that DH has a germ phobia so no way he could do it & honestly I would spend the whole time saying "WTF! This is bloody disgusting" .

I think it could be possible that poo has built up over a night or two but the smell is more then that.