Barb, is this floured or wet-battered- can't tell about the plan.
Amount of oil depends on pan frying vs deep frying and how much you need to do at once; if this is a sit down meal, for example, all the fish has to be cooked at almost the same time; if basket by basket for sale, not so much at once. Fried fish DOES NOT hold.
The mac and cheese, you need to assemble ahead but cook day of. It is not safe to cool large amounts cooked and reheat- it cools too slowly, and reheats too slowly in the middle, and has WAY to much time for bacterial growth.
Look at this off site article.