Oh, I see now that you are in the UK. The big thing when it comes to carpet is the thickness of the padding underneath and the thickness of the carpet pile itself. If you get thick carpet pile, you have to get a fancier vacuum . My hubby and I learned that the hard way. We got super high pile carpet.... And then our basic vacuum wouldn't work anymore, so we had to buy a shark vacuum. It's a great vacuum, don't get me wrong.... Just wouldn't have been needed with a different carpet thickness
Regarding the anti stain carpet, id look up reviews on it, as reviews are often very helpful ( probably see if a mum blogger has a review, to see how parents like it
I don't have experience with kids and carpet. But things like little green are a great idea , even if your carpet is anti stain ( helpful for bathmats, sofas, cloth interior of the car .... But definitely not with car seat) . And not sure what anti stain means ( I've heard of LifeProof) .