My parents are lovely people but they live in squalor and always have. The house is full of animals; several cats, an enormous long-haired dog, parrots flying free range and that's just in the house. In the paddock they have all manner of creatures. There is grime and dirt everywhere. Everyone wears their shoes inside as if they didn't their socks would be black within minutes from the dirt on the floor. It was always like this when I was growing up and I thought it was pretty normal until I moved away at 18 and realised no one else lived in a house like this. Until recent years they've been healthy and able-bodied. My dad had a stroke a couple of years ago so is a bit more sedentary now but it's no worse than usual. They could afford a cleaner if they wanted one.
Anyway it was never a massive deal, just how they choose to live. A bit embarrassing taking my now husband there for the first time but meh, whatever. They live 200 miles away and we only visit a few times a year. They live in a very rural location, there are no hotels nearby so we just stay there and put up with it.
We now have an 8 month DD. Last time we took her she was 3 months old and we just held her the whole time and insisted that the massive, untrained dog was always shut away and the birds caged. We're visiting again in a couple of months and DD will almost certainly be crawling by then. Even now she doesn't really like being held and likes sitting on the floor surrounded by toys. I don't know how we'll keep her off the floor for 3 days.
The main problem is that DM doesn't think the house is dirty, will be incredibly offended at the suggestion that it is and will certainly cry. I have tried to gently suggest the place could do with a bit of a clean in the past and it did not go well. I can't stand the idea of upsetting her like that 
But I genuinely believe DD could be at risk crawling around there. They come straight in from walking around in shit in the paddock and shoes stay on. How can I raise this in the most sensitive way?