Thanks for all the advice.
We now have a trip planned both walking and riding (we're taking the CAR! too) staying near Loch Lomond, then going Bute, Islay, Jura and stopping off near Alston (not Scotland) on the way home. We have a habit of enjoying seeing huge areas of countryside and as a result spending far too long in the car when we go away so have tried to limit the car time on this trip.