The most kid and pet friendly couch material is leather. So far our blue leather couch has coped with 18 years of toddlers falling asleep and weeing on it, cat vomit, Easter eggs melting between the cushions, spilt milk, spilt orange juice, spilt red wine, spilt coffee, and muddy dog paws. It just wipes clean. Our white leather chair is just as durable and is now 24 years old and just starting to look grubby. So go with beige or cream if you want. It would be a lovely choice, just make sure it is leather. Black or mid or dark brown would also look lovely with that beautiful rug but I think lighter colours would look fresher. Don't be at all scared to use light coloured leather.

I have two dark grey sofas and I am eager to lose them as I can't find anything too complementary for the either! They seemed like a good neutral tone at the time but being dark they have showed up lots of stains (young kids). Your question was cut off but if you wanted to add a rug or furniture, I might suggest an orange/rust tone or even a red? But the colours of your walls will have a big impact... Hope this helps. :)

I think you are on the right track with a tan colour... Will mix great with the greys. I'm a huge fan of a lovely aged leather. A black/dark grey pattern rug could add some interest and texture to the space as seen in below images. If you go a tan then consider the colour of your tv unit & coffee table to be different as to not look too matchy and another colour for these other than the same as sofa.

It's really pretty! But it is still so expensive I am sorry to say. I mean I just bought a pristine leather sofa from a grandmother off eBay for $300. I do this every other year and only get really good items, just waiting for the right thing.