Yeah, but this also means all flora and fauna are larger due to the increased gravity, this also means they are stronger. So technically even the humans/scavengers would be giants compared to us, and the book already has them being nearly as tall as Clay’s shoulder. However, we’re not given the moons sizes, we’re just assuming these are all the same size as our current moon, and therefore, similar gravitational pull. My guess is they would all orbit differently as well, with the third moon being the smallest and furthest away from the planet given how it is rarely seen with the other two moons. (I don’t remember how the brightest night is described as).
Assuming the moons are different sizes, it would be hard to know how massive the planet actually is since we don’t know the mass of each moon. Mars has 2 moons but they are smaller than our moon, in fact they’re considered to be the smallest moons in the system. Mars also isn’t as massive as earth so this makes sense. We don’t even know how close the moons orbit the planet.