Basically, the definition of wish is a desire for something. Under that definition, even Jesus Christ expressed wishes at times: “O Jerusalem, Jerusalem, killing the prophets and stoning those who are sent to you! How often would I have gathered your children together as a hen gathers her brood under her wings, and you would not!” (Lk 13:34).
Sometimes people express the hope that they have that certain wishes will be granted by stating the wish while doing some specific act (e.g., blowing out candles, watching a shooting star, pitching coins into a fountain). Unless there is a belief that the action will magically bring about the wish, which most people do not entertain, there is no superstition involved (cf. CCC 2111). Certainly, there is no idolatry.