MrK – What do you mean by kids? Cardrona is a tiny village between Glentress and innerleithen and the main road between the two is not something you'd like your kids to cycle along.. if built properly, a pump track can be made to last – I do agree it wouldn't get used too much after the initial interest tho.
Northwind – Bollox, GT has a purpose built skills loop for beginners/kids a new green route especially built for families/kids, and easy blue route that most 7yr olds could do (accompanied by an adult) and the red is a scalextrix track. not to mention the 3 easy free ride trails and the weekend kids club run by the Hub.