If I were my house, I'd go with replacing the carpet and pad.
Hardwood doesn't need any maintenance other than normal cleaning, and that can be done with a damp sponge mop.
Both kinds of floors can be permanently damaged, but there are two things you really should know before making your purchase decision.
1. Woods that have a lot of yellow, red or brown colouration to them (like cedar, Southern Yellow Pine, red oak, redwood, etc.) tend to contain a lot of tannin. If tannin comes into contact with iron, it forms a black compound that will stain the wood permanently. This black dye was used in the middle ages as ink, and is called "Iron Gall Ink. The most common way this affects hardwood floors is when people overwater a plant that's sitting right on the hardwood floor. The water will percolate through the soil picking up iron ions from the soil as it does. If any of that water leaks out on the floor and comes into contact with the bare wood, the tannin in the wood will react with the iron ions in the water to leave a black stain on the wood. You often see circular black stains on hardwood floors, and that tells you there was a potted plant once standing where that black circle is.
So, if you opt for hardwood, and you're concerned about plants on the floor, then I'd try to get a hardwood with a very light colour, indicating a low tannin content. Tannic acid is brown in colour, so generally white woods have a low tannin content.
2. If you buy a carpet, buy a solution dyed nylon carpet.
DuPont has spent a king's ransom trying to make their Antron nylon stain resistant, and that's evidenced by the $40+/square yard price tag on StainMaster carpets. Many other carpet mills are now producing solution dyed nylon carpet. That means that:
INSTEAD of drawing the transluscent nylon plastic into a fiber and then dying it the desired colour using conventional dying techniques
THEY add tiny coloured particles (called "pigments") into the molten nylon plastic before drawing it into a fiber, and then dying the coloured nylon fiber with a clear and colourless dye.
The resulting nylon fiber is double protected. The clear colourless dye occupies all of the polar amide sites on the surface of the plastic which is what makes nylon susceptible to water based stains, so water based liquids don't see any polar sites on the nylon surface they're attracted to. Secondly, even if there were unoccupied amide sites on the nylon and a coloured water based liquid were attracted to those sites, because it's on the surface of the nylon, it could be rendered colourless by applying bleach. That bleach won't affect the colour of the carpet because the fiber gets it's colour from the pigments encased inside it, very much like raisins inside raisin bread.
As a result, bleach straight out of the jug won't harm solution dyed nylon fiber. That's cuz the pigments are encased in nylon, so the liquid bleach never comes into contact with them. I can't say whether or not the bleach would break down the clear colourless dye on the outside of the solution dyed fiber. If it did, then that area would now be more susceptible to staining by water based liquids, but bleach could still be used to remove another stain from that same spot.
And, that simple system makes far more sense to me than trying to make the plastic more stain resistant as DuPont has been trying relatively unsuccessfully to do for decades.
Nylon is the strongest fiber that carpet is made of, and a loop has a natural resilience that no other geometric shape can match. So, over 90 percent of the commercial carpet sold is made of level loop nylon fiber. If you buy a level loop carpet made from solution dyed nylon fiber, you're getting a very long wearing carpet that you can use bleach straight out of the jug on to remove otherwise impossible stains without harming the carpet whatsoever.
I own a small apartment block, and I install solution dyed level loop nylon carpets in every one of my apartments when the living room carpet needs to be replaced. I buy the Shaw "Franchise" series level loop nylon carpet in the "Starry Night" blueish colour. Shaw makes a variety of other solution dyed nylon level loop commercial carpets, including their "Reward Power" series.
So far as I know, solution dyed nylon fiber is only being used to make level loop commercial carpet. You can't buy a residential carpet in a berber or saxony made of solution dyed nylon yet.
And, I expect it wouldn't be lost on you that you can prove to yourself that everything I'm saying is correct by spending $3 on one of those door mat size samples of solution dyed nylon carpet and torturing it with cherry Koolaid and bleach straight out of the jug.
You don't need to know the rest:
I like to think I know a fair bit about cleaning carpets, and the vaccuuming and shampoo'ing you're doing is excellent to extend the carpet's life as long as possible. You should be aware, however, of a popular misconception, which is that shampooing a carpet gets it cleaner than vaccuuming. The two cleaning methods are not in competition. Vaccuuming will only remove SOLID particles of soil from the carpet; it won't remove liquid spills. Shampoo'ing will remove liquid spills by dissolving the liquid in water and then sucking that soiled water out of the carpet; it won't remove solid soils effectively. To prove this, just try cleaning sand off wet feet and dry feet next time you're at the beach. When your foot is wet, the film of water on your skin holds onto the sand on your skin. It's just the same inside a carpet. If the sand or soil particle is sitting on the surface, then the suction of the shampoo'er will probably remove it from the carpet. However, if the sand grain has fallen into the pile of the carpet, the water film will hold onto it just like the sand on wet feet, and that sand grain is likely to stay behind in that carpet after shampoo'ing. It would be much more effectively removed by a vaccuum cleaner.
So, the bottom line is: Regular vaccuuming with a vaccuum cleaner that vibrates the carpet pile while drawing airflow through the carpet is most effective at removing solid soils from the carpet. Shampooing is really only effective at removing liquid spills from the carpet. To get your carpet clean, vaccuum it regularily and vaccuum before shampooing.
You can also use a wet/dry shop-style vaccuum cleaner to remove liquid spills from your carpet. You can't shampoo the whole carpet with a wet/dry vaccuum cleaner, but you can certainly use it to remove still wet or dried up liquid spills.
Don't know if this helps you make your decision.