Don't change the lyrics. The word itself is not offensive and you will be educating the young people by showing that many words have different meanings, depending on context. If the teacher objects, I would tell him/her to grow up and stop being so infantile.

There are a whole range of jokes, songs, etc. that depend on a play on words to achieve puns, double-entendre and the like. But there are also those, as in your example, which innocently raise a giggle. The language would be poorer if valid words and meanings were to be forced out by silliness. Just as beauty is in the eye of the beholder, rudeness and offense is often in the mind of the listener.

DC