Even you have to pay 7 Euros to visit the abbey, and we have had serious doubt we went for it and didn't regret. The lanscape is great, the "Jardins de merveille" give the unique sensation of peace and calm.
As the wind could blow pretty powerfull, it's safe to take a jacket and a cap. take sunglasses and head-protection as the sun reflected from the water (when it is high water) and the direct sun could harm you. If you decide to follow the path on foot up to the Mont.
Photo Equipment: Take a tripod for the photo camera, you can take good night-shots of the abbey.
Camping/Beach/Outdoor Gear: Camping is safe and nice, but of course you have to have warm coats on you.