Motza’ei Shabbos is not a Ra’ya at all. The Minhag is to put it out by dipping it into the wine, not just because it is the easiest option other than blowing it out. However, there is an Inyan from the Arizal not to blow out a candle with your breath. Some people don’t blow, but would say PPPurim-PPesach on it until it goes out.
Just because something was done many years ago by whoever, that doesn’t make it Avoda Zara. Avoda Zara is exactly that – idol worship. You are not worshiping anyone by blowing out a candle. Nor would it be Darkei Emori, for it is not being done as a superstition, only as a celebration. However, you might bump into the problem of Chukos Akum. Being that it is only for fun and is not meant as anything serious, I can hear a big Makom Lehakol.
So, as all good threads go:
Ask your …
And, of course, let us know the response.