Just like the optimal amount of fraud is nonzero (https://www.bitsaboutmoney.com/archive/optimal-amount-of-fra...), the optimal number of dead children is too. A child doesn't have a meaningfully greater chance of dying on an airplane than an adult, so what this question is really asking (while crudely attempting to tug on the heartstrings) is whether we're willing to tolerate people dying in order to keep planes flying. The answer is obviously yes. We don't cancel all flights globally when a plane crashes and everyone dies, because we suddenly can't tolerate the risk anymore.