Hello All,
We have had coding classes running in Dundee for a couple of years now and they have proved really popular. Scratch in particular is very successful with the 8-12yr old age group. We run our classes independently of Code Club but have used their resources in the past, Coder Dojo is also worth a look as is Code Academy.
As far as volunteers go, we have had most success approaching local students (many of whom have a good coding knowledge from courses they are doing). At the moment we have 2 students from Abertay University's Ethical Hacking Society who have been great.
As has been mentioned Scratch is relatively easy to pick up and there are lots of walk through tutorials on YouTube that could be used to get started (even I have mastered the basics!).
Scratch is also free to install and from a trustworthy source so hopefully doesn't pose too many difficulties to get installed or convince others to install on PCs.
Hope that helps.
Best wishes,
Kevin