The Scottish National Anthem should be Wild Mountain Thyme. Everyone likes this song and it has no contraversial parts.
There is some contention over lyrics though - 'purple heather' or 'bloomin' heather', 'I would surely find another' or 'I would surely find no other' (big difference)
If I was to pick a Burns song I would go for Green Grow the Rashes (rushes) O.
Scotland - Land of the lousy weather (you should try living in Wales ! )