Building rest days into a trip without feeling like they are wasted

My itineraries tend to alternate long sightseeing days with other long sightseeing days until everyone is exhausted. I want to build a real rest day into a two-week trip, but the word ‘rest’ starts sounding like a wasted hotel night. Perhaps a slow breakfast, laundry and wandering a local market are exactly what makes the other days enjoyable. How do you schedule recovery without treating it as another list of things to accomplish?