Walking on the carpet, I would have said to them to take their shoes off prior to coming into the carpeted area. One thing I have learnt is that never assume anything about another person. Not everyone shares the same rules as us or have the same opinions as us, they can seem rude in our minds, but it doesn't necessarily make it so. To some walking on carpet isn't considered rude so if that is the case, then they won't give it a thought. I always take my shoes off in other peoples homes because it was how I was raised. Doesn't mean other people were though and they could genuinely not have friends with those rules so don't give it a thought. You'd think given the colour they would think more, but clearly not. It's unfortunate and infuriating but where were you when this happened? Wouldn't you have been right there anyway? I would have been on that in a shot always expecting someone to walk on it. Even if it was unintentional, I would still be extra alert should someone just simply forget.

As for your washroom, I really wouldn't lose any sleep over it. If someone needs to pee, they need to pee. Who cares if they pee regular as long as they are polite and clean up after themselves. My last house had 1 bathroom that is it. No en-suite and no 2 piece. If anyone needed to pee they were always in our family bathroom and had to walk through my house but really, I'm not going to turn away someone who needs to go, that just seems petty. Just my opinion though.

Some people actually need direction. Whether we want to parent them or not, or feel like we are always having to tell people how to have common sense, it doesn't change the way people are. Have no expectations from these people and then you won't be disappointed. We can't control others, only how we react to them and some people will just be forever clueless. Get a hall mat to go over the cream carpet to prevent dirty foot prints, or be on them like flies on s&^t before something happens. And if they are entering your home beyond daycare boundaries then flat out tell them that they are not to go beyond a certain point. As for the bathroom use...I'd just let it go. Far more things to worry about.