Cook macaroni according to package directions. Preheat oven to 350°.
Meanwhile, in a large bowl, whisk the eggs, milk, butter, mustard, seasoned salt and pepper until combined. Stir in the process cheese and 1-½ cups of each cheddar cheese.
Drain macaroni; stir into cheese mixture. Pour into a greased 3-qt. baking dish. Top with remaining cheeses. Bake, uncovered, until cheese is melted and edges are bubbly, 25-30 minutes.
