The flu death rate in the 0-4 age bracket for the 2022-2023 was 1.2 per 100k, compared to 26.6 per 100k for the 65+ age bracket. Meanwhile, the death rate of the 1-4 age bracket [different sources; different buckets] was only 28 per 100k, compared to 2000 per 100k for ages 65-74 or 15,000 per 100k for ages 85+.
So, flu deaths are a larger percentage of child deaths than than elder deaths, even though most people who die of the flu are old. The answer to "How can we most readily lower child mortality?" is always going to be "Keep infectious diseases under control."
The bigger thing is that the IFR differs dramatically based on age, and eventually you either die from something else or get old.
If it weren't for the IFR going up with age, you'd still have a very low lifetime chance of dying from the flu.