Preheat oven to 350°. Spray 3-quart baking dish with no-stick cooking spray; set aside.
Cover potatoes with water in 4-quart saucepot; bring to a boil over medium-high heat. Reduce heat and simmer 15 minutes or until potatoes are very tender; drain. Stir in 2 Tbsp. Hellmann's® or Best Foods® Real Mayonnaise and 1/2 cup milk. Mash potatoes, then set aside and keep warm.
Melt Country Crock® Spread in another 4-quart saucepot over medium heat and stir in flour with wire whisk until blended. Slowly stir in remaining 1-1/2 cups milk and bring just to the boiling point, stirring frequently. Stir in wine and heavy cream and cook, stirring frequently, until slightly thickened. Stir in cheese, mustard and remaining 2 Tbsp. Hellmann's® or Best Foods® Real Mayonnaise. Cook 5 minutes over low heat, stirring frequently, until cheese is melted. Stir in scallops, shrimp, fillets, spinach and peas. Cook, stirring occasionally, 3 minutes or until shrimp just start to turn pink.
Turn fish mixture into prepared baking dish. Pipe or spoon on warm mashed potatoes.
Bake 30 minutes or until bubbling and fish is cooked.