My wife and I arrive in Paris from the US on Sunday, Sept. 14 around 9:30AM. We're taking a taxi from CDG to our hotel in St. Germain des Pres. I figured we'd drop our bags at the hotel (before check-in time) and wander arournd St. Germain, making our way to the Isle de la Cite to see Sainte-Chapelle & the Notre Dame.
Question #1: Do you recommend purchasing tickets in advance?
Question #2: Will the lines for security / entrance be very long at that time of day / season?
Thanks much for any advice you can impart!