Well, your number of children is linear, but your number of descendants is exponential. For the CS students, what this means is that the number of children you have personally, even assuming they all reproduce, rapidly becomes immaterial next to the number of your descendants.
The only reason having more children might be beneficial is if it significantly increases the odds that they personally, or their children successfully reproduce. If you have some other way of boosting those odds -- say, by being a successful parent to a smaller number of children -- that's just as good in the long run.
But each generation only carries half the DNA of the previous one. So after 5 generations there is a vanishingly small chance that anyone after that will still carry your DNA, with the exception of male lineage -- there you know that the Y chromosome has made it through.
The only reason having more children might be beneficial is if it significantly increases the odds that they personally, or their children successfully reproduce. If you have some other way of boosting those odds -- say, by being a successful parent to a smaller number of children -- that's just as good in the long run.