You don't want to give your child false notions of how the world works. This might actually be Assur, in the same way we aren't supposed to give credence to untrue entities, or work with untrue, non-existent powers. That is what Darkei Emori is all about.
One may chant Shabriri Briri, but may not dance for the Cholent to work out. The difference is that the former exists and the latter does not. If Hashem gave them room to do something then recognizing that is fine. If he didn't, then by giving other entities space in our lives that were not meant to be, you are giving away Hashem's ownership. See Maharal, Tiferes Yisroel 46 for a related concept.
Although you aren't following a superstition yourself, you would be doing something worse, actively training someone to believe it.
More importantly, the Pasuk says שאל אביך ויגדך, ask your father and he will tell you. The ability of the Torah to go over to the next generation depends on how much your child will trust you. How will he be able to trust you on everything else once he finds this not to be true.