Thanks, question resolved.

I took the paintings into my local auction house- I've been going there for years and respect and trust the auctioneer.  He told me the paintings were around 15-25 years old, aboriginal, and from the Northern Territory.  

He said he personally liked them very much- the colours are bright, a lot of time and effort went into the larger one particularly, and they have recognisable stories/symbols.  However, the problem is that since there are no signatures, gallery/auction labels, backstories etc the value is restricted to essentially whatever someone is willing to pay because they like them as pretty pictures to hang up at home.