Very interesting links to fascinating projects.

I've done some similar work here in UK with primary school pupils and found that a great way in was to start from a cheeky, formulaic kids' song (Three crows sat upon a wall x 3, On a cold and frosty morning). Pupils happily engaged with adding to the number of crows and their subsequent problems -- the original has verses like 'The first crow couldnae flee/fly at a/all', On a cold and frosty morning'.

But I also had a great experience -- over an 8 week period (including dancing session) -- of constructing a song with a group of 10 year-olds -- based on the story of Mary, Queen of Scots and her sad demise. This was included in a script (put together by the class teacher) which we eventually performed in Stirling Castle, together with authentic dances from the period which had been taught by an accredited teacher.
The whole project was supported by funds made available to The Traditional Music and Song Association of Scotland (TMSA) by the Scottish Arts Council.

Bottom line is that children love singing and inventing, and that anyone who can access funding from government sources should be applauded.

All success to those involved!