I certainly would sing wee and would not think of changing it. While I would never attempt a Scots rendition of a song, an occasional word that we all know anyway is not going to hurt anyone. And I should sing in Scots anyway because I am descended from all the royal Stewarts. In fact I should wear the Stewart plaid whilst singing the auld Scots songs. But I will refrain as I do not have an ear for accents, dialects etc.