I was told that the reason why blowing out candles is forbidden is because of something related to shaidim. Is the same issue relevant when blowing in other contexts, or only blowing out candles. For example, is it a problem for a child to blow bubbles from a bubble wand?
The idea of not blowing out a candle is based on a Brayso brought in the Kol Bo siman 118, that a person who blows out a candle can cause himself to become “nichfe”. It is not clear what this ailment is, and there are those who say that it is epilepsy. Regarding your question, in general, when it comes to such ideas, which are based on things we don’t understand, we are only careful about them in the exact regard that they are written, but not for other things. Therefore there is no issue with blowing bubbles, blowing up a balloon, or anything else but blowing out a flame.
See Rashi Shabbos 61a D:H nichfe, Tzitz Eliezer 13-35(1).