If a child is still legally the responsibility of its parents or guardians then the guardians would be responsible for making sure they vote in the best interests of the child. See also what’s happening in America (my country of residence) - a lot of fascists are voting in ways that will directly harm their lives. I could make an argument those decisions harm the children as well.
I feel like the line of questioning is a trying to head down a reductio ad absurdum path..