Christian Constant never closes. Neither do the fancy chains -- Lenôtre, Ladurée, Dalloyau, Hédiard. Pichard is open in August. You'll find that the week before August 15 is a very quiet one and the city looks, in some places, abandoned.
Absolutely. That's why I usually stay in August. Whoever is there has some time on their hands, good encounters, good times. But if you come for shopping, the possibilities are significantly diminished.