They didn't take age of kids into account. But I agree with your reasoning, so I'd expect that there was a large difference for below 45 kids vs. no kids, and s

They didn't take age of kids into account. But I agree with your reasoning, so I'd expect that there was a large difference for below 45 kids vs. no kids, and smaller difference for above 45. But no, in both age groups, kids vs. no kids had absolutely no effect.