As far as I'm concerned kids are the most important people and we're just keeping the seats warm for them.
I always hear statements like this thrown around in various contexts, and while on the surface it sounds admirable, it's really not accurate at all.
The most important people on the planet are those with the knowledge, skills and the actual power and means to accomplish what needs to be done. Without the core set of human adults that actually feed our population, keep it safe, fix broken and unhealthy bodies and the like, there would be no children. Or if there were children they would mostly be dying.
Also based on that logic, the instant a "child" becomes an adult sitting in that seat you kept warm for them, they're not important anymore, and the real focus is immediately on people younger than them. Unless there's like a grace period of importance - say you get 5 years of still being most important after you're no longer a child? See what I mean?
Obviously we need children, and we want the human race to continue and all that, and to provide for them a planet better than the one we started with and with more opportunities, but saying kids are the most important people sounds good in a Whitney Houston song, but isn't very realistic.