I can't think of a chippy anywhere near the A590 off the top of my head. Plenty in Kendal and one in Coniston but a little out of your way.
Not a huge amount of scree around in the Duddon valley nor the Furness fells but there is some nonetheless. Of course I have no way of knowing where the course will take us so can't really advise but I'm sure you will encounter some loose rock at some point in time!