I would say that most of the beach from at least the Casares roundabout (east of Duquesa) to Punta Paloma is great! I think the beaches here are mostly blue flag. There are many good chiringuitos - both east and west of Duquesa port (from La Sal at Casares roundabout to Tubalitas at Punta Paloma) to choose from. And more!
There is a deli/grocery in Monte Duquesa, down the hill from Duquesa Village (near bottom of the hill, west side), Armstrongs, that sell basic commodities and also a small supermarket in the port that sells fresh bread - but you also have Supersol and Mercadona supermarkets in Sabinillas that sell freshly baked bread.
Enjoy your holiday!