A rough outline of the route is available on the attached map. Both routes (junior and senior) take in beach and coastal trails. Studs but not spikes recommended (road shoes would be OK too).
Details of Whitesands car park can be found on here:
Please be aware that the start and end of the Dunbar leg is pretty "spartan" there is a public toilet block that should be open for the event but there is very little else in the nature of changing/shelter. Bring extra layers to keep warm before and after :-)