I'd also suggest if you have them, that you could portion the mixture into individual baking dishes. Just do a little olive oil and garlic in each one to start. Then leave them covered in the refridgerator on hold while you, say...serve a nice salad first. When you put the salads in front of each person, that's the time to pop the casserole(s) into the preheated oven since bake time only takes between 10 minutes (if shrimp is already cooked) or 15 minutes (if they're raw).
So, by the time folks are finished with the salad, the main dish is ready to serve nice and hot from oven to table. Yum.
A little garlic bread might be nice. My chilled avocado soup is another good starter, then you could serve a salad with dinner as the 'vegetable."
Oh, and make sure you know that guests are okay with shrimp in advance of the get-together.