From the horses mouth:
In The Essential Ewan MacColl Song Book Peggy gives the word as 'Quaenes' with the note "girls or women" and in 'Travellers Songs From England and Scotland' the glossary gives 'quaen' as "a young woman, (Northeast Scots dialect).
As far as MacColl as an artist was concerned, he was arguably the best and most prolific songwriter in the whole of the revival; as Hamish Henderson said "Anybody who could write a song as good as The Joy of Living could be forgiven anything".
Any quirks and idiosyncrasies he might have had were more than made up for by the fact that while other folk 'superstars' were getting on with their careers (and only taking time off to snide at MacColl), he spent an evening a week for ten years helping younger and lesser experienced singers to develop. His and Peggy's generosity with their time, advice and material left all the shit-spreading, snide farts standing - that was my experience anyway.   
Jim Carroll