I am french, I just come back from Seychelles and I have good plans for you
-to hire a car with good prices in Praslin et Mahé (we had our car for 40euros per day!!! we visited a lot of beaches),
-you can see photos of excursions from Mahé (with Raymond) and La Digue (if you want to benefit from your voyage, I strongly advise you to visit the small Islands (Félicité, Coco...), we swam with fish :))), they organize also fishing
2) don't forget : sun lotion, cap, cotton's tee-shirt, camera (under water), lotion for mosquitos.