The short answer: Kids and pets are two totally different things. Most carpets will be fine with kids. With pets, the real issue is that pets go to the bathroom on the carpet sometimes. For that, a carpet with a special pet backing helps. A moisture-barrier pad, in my opinion, doesn't do much and can actually make things worse.
Kids
Most carpets will be fine with kids. I guess kids can have accidents on the carpet too, but for the most part, that's a pet issue.
Pets
The only reason you have an issue with pets is that pets go to the bathroom on the carpet sometimes. There are some carpets with a special pet backing that keeps moisture from getting through the carpet and into the padding. Those do help with pets.
Do I need a moisture-barrier pad?
That brings up padding and the moisture barrier on the padding. Some places really push the moisture barrier on the pad. My belief is that moisture-barrier pads don't really do all that much, and here's my reasoning.
For liquid to reach your pad, there has to be enough of it to go through the carpet fiber, through the primary backing, through the glue that holds the carpet together, and through the secondary backing. Then it hits the padding.
- With a moisture-barrier pad, that liquid is just hitting a plastic film. At that point it spreads out on the film. That spreads more damaging liquid, and in some cases almost acidic urine, over a bigger area of the back of the carpet.
- Without a moisture barrier, the liquid just goes straight down into the padding. In that case, you could just pull up the carpet and replace that section of padding.
When it hits a moisture barrier, it spreads out and damages a larger part of the carpet itself, which to me is kind of a negative. That's my opinion on moisture-barrier padding.
For more on choosing pad, see Does Carpet Pad Really Matter?
Have pets and want to talk it through? Come see us in Provo or Lehi. We offer free measuring and free estimates.