I think children need to hear their fathers tell their mothers that they are beautiful. Fathers need to say it out loud. They need to say to their wives and to their children “look how beautiful imah is” even when she is not dressed up for a chasunah, even when she is not wearing make-up, even when she is not looking her best.
Parents need to instill in their children that beauty is not necessarily equal to a cover model, or a size two, or perfection. But beauty comes from within, it could be the smile the lights up the room, the compassionate eyes, or something else that a parent can point out to a child.