the materialism part, maybe by teaching some basic physics? pointing out how everything conforms to law, gravity is a simple one to explain i think.

for the dialectics part, i like boiling it down to “things as a process”. maybe a good way to teach it is by growing plants, telling the kid to observe the plant each day, watch the gradual changes, use the different phenological stages of the plant to explain how imperceptive quantitative changes lead to qualitative changes.

i don’t have a kid so idk if it would work, but this is how i imagined i would do it. obviously it’s a process, everyday talk about it and such until the kid internalizes it.