Cook macaroni according to package directions. Meanwhile, in a large bowl, whisk the eggs, milk, butter, mustard, seasoned salt and pepper until combined. Stir in the process cheese and 1-1/2 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, at 350° for 25-30 minutes or until cheese is melted and edges are bubbly.