Cook and drain the macaroni.
Turn the Crockpot on low. Add the cooked and drained macaroni, the two different milks, salt, melted butter and all but 1 cup of the shredded cheese. Stir together, then sprinkle the rest of the cheese on top. Cover and cook 2-4 hours.
Check a bit before your party and if there's too much liquid on the bottom, stir it together.