If you can afford it, ditch FSS and get something that will hold up and provide better buffering power.
ADA Aquasoil, UP Aqua Shrimp Sand, Azoo Plant Grower Bed, among others.
Be sure to search around the forum to see what everyone uses as a remineralizing product. There are several that are great and clean. Shirakura Ca+, Mosura Mineral Plus Ultra, Salty Shrimp, etc.
I'd let the tank run 4-6 weeks - even if it's cycled - to make sure there are tons of goodies ready when the shrimp arrive.