I would take a leaf out of Judy Martin's book and the way she has her log cabins quilted (ie SITD or straight lines in the dark and freeform, eg feathers in the light.) I think this differentiates nicely between the two areas and enhances the design. So I would SITD down either side of the stacks of coins and between every few, depending on what your batting requires, then do a freeform, viney type thing (technical term :mrgreen: !) in the sashing. :-D
PS - I'd use a blending thread, possibly variegated for the SITD and a white for the sashing.