We are attending a conert at La Sainte Chapelle Friday evening May 6th at 19:00, Piano Quartets. I'm wondering how long the concert will be so we know what time to make dinner reservations. We will likely be dining in the general area, perhaps Mon Vieil Ami or maybe even La Tour d'Argent. Is it safe to assume a reservation at 21:00? Thanks in advance for your help.