Stewart,
Having driven on the sand of the Sahara in Morocco (Land Rover), I would go 
with the wider tire. The sand is fine and you will sink in easily, so the 
more floatation, the better. And I would imagine the all-terrain tire would 
be more suitable more of the time-when you�re on pavement-then the knarly 
mud-terrains.
Have fun, sounds like it will be easy to.

Ra�l Cisneros
87 Syncro westy
86 Syncro GL