Get the professional sander guys in to repair the living areas and kitchen but don't go too dark with the stain as it will kill the lovely grain in the matai. I'm thinking a couple of tones richer than the timber knots showing in your photo, definitely no yellow tone at all. In NZ stepping on to carpet especially in a kiwi winter is so much nicer than a cold floor board shock!!! A nice area rug for the lounge and you're done.

If the flooring guy doesn't have any suggestions, he's not a flooring professional. Fire him and hire a real contractor who can deal with subsidence and settling issues.

Sanded and polished timber floors have a evergreen classic appeal that never goes out of fashion. Carpet and other floor coverings do have a tendency to have a style that is relevant to a particular period in time. Have you ever walked into a home and thought the carpet, lino or tiles were from the 60s, 70s or 80s? Natural timber floors never date and you can easily update the look of your home with warming floor rugs and furnishings. Carpeted homes may pose problems for Asthmatics and those that suffer from allergies. There are a few environmentally friendly coatings available if you do choose to sand and polish your floors. This link will offer some insight into your floor coating options. http://budgetfloorsanding.com.au/timber-floor-finishes/ All the best with making your decision

Sorry for the delay....well I still haven't quite got to the floor yet. I have friends and family advising that black would show up every bit of dust etc and one friend who had a shiny black floor and felt that she was forever mopping, and if the light shone on the floor on the wrong angle you could see where the mop had been. I think this would frustrate me too much especially with young children and a cat so I think a whitewash look could be a good option, or reclaimed battered timber perhaps.......see why I haven't chosen the floor yet. Lol. You could always go a black but a weathered matt reclaimed timber that could look good too. Good luck!