Amanjena will be perfect, it's outside of the mayhem but with enough proximity to the city center that you have options. Another alternative for relaxation is Kasbah Tamadot, Richard Branson's property ~1 hr outside of Marrakech. Also lovely.

And if you want to relax on the coast, La Sultana Oualidia is a small, private, stunning boutique resort on the coast that the royal family has frequented. It's about 3 hrs drive from Marrakech, so that may be too far.