Mine have the same carpet as everywhere else but that is basically "nice" carpet and so far so good. You can get milky pukes in the early days as you burp them after a night feed, depending where you do that. If they have a tummy bug they might puke down your back and have some land on the floor etc! And as older children that could happen too.
Regarding things they play with, if you dont use the room to play in with things like pens, paint and playdough (which comes out of carpet anyway as do most pens and paint, depending!) then you should be fine. My son got some bath crayons on his carpet, that lifted out fine.
Having said all that, and this may identify me in real life because I've told anyone who will listen, but I actually had a bottle of OPI nail polish break on my bedroom carpet - of all colours it had to be Lincoln Park After Dark which is vampy burgundy almost black type colour - and it came out!!! It dried there overnight (drunk, DH wouldn't entertain the idea of me cleaning it up there and then at 2am) and it ALL came up! So nail polish remover does what it says on the tin!
My carpet is amazing though! Its wool blend, apparently, and I think that little bit of nylon makes all the difference so you might consider that.
Having said that, the worst are those sisal and grassy type fibres - very absorbant but hard to get the fluid out again! Hard wearing from a traffic point of view but bad for liquids.
The only thing with wool also is can you Vax it using warm water or would it shrink? I think its nice to have the option to rug doctor or Vax a carpet with kids - if not for stains, then for smells...