Hi, Angelle. Can you get frozen shrimp, rather than thawed? I would not recommend re-freezing thawed shrimp, but unless the place you buy it from buys it fresh off the boat every morning, just about all fish and shellfish is frozen either at sea or at the dock.
You can buy frozen shrimp in advance, thaw the day you want to shell them, then cook them the next day. Or, you can buy the butcher's thawed shrimp, shell them that day, and cook them the next day. They will keep fine for a day, even two, but keep them very cold as much as possible. HTH.
The trouble with eating Italian food is that five or six days later you're hungry again. ~ George Miller