It's usually a mistake to look for "meanings" or "stories behind" popular songs written by prolific, professional songwriters; which is what we have here. It's just a song, written for money, using tried and tested formulae (including "Allandale", which featured in other pop songs of the day, probably written by people who didn't know whether it was in high or low country in any case; "highland cots" were as commonplace in such songs as fair morns and clear skies. It's a wonder that there isn't a May Morning as well). By all means invent your own, personal "meaning" for it: but that is all it will be.

The song was written in common time. The Copper family sing it in a mix of 5/4, 6/4 and 3/2. Revival performers who have recorded arrangements of their set have tended to simplify it down to a basic waltz rhythm. Take your pick, but be aware that any judgement you make will be subjective. To my mind, the Copper modification can't be bettered; but that's a personal opinion.