This was a good shot to do a black and white edit on. Dunes are never colorful and often look dead. So I think the edit helps the overall pic. I only wish the clouds were more distinct.
I think the scene itself is lovely, and I don't have any issue with the sky. It's just bit on the dark side and a bit flat. For all the obvious sunshine here it still manages to convey an "overcast" feel - if that is what you were after, then you have succeeded.
However, maybe 5-10% lighter and a contrast boost of about the same might do this one wonders. I understand increasing the contrast might be problematic with the larger shrub; you don't want to lose shadow detail. Still worth trying, though - and the sky should be a non-factor. If anything the clouds will punch out a little better with more contrast. My two cents!