Whisk first 8 ingredients in bowl to blend. Season dressing with salt and pepper. (Can be made 1 day ahead; chill. Bring to room temperature before using.) Combine clams, mussels, and wine in large wide pot. Cover tightly; cook over high heat until clams and mussels open, about 8 minutes (discard any clams and mussels that do not open). Using slotted spoon, transfer clams and mussels to very large bowl. Strain cooking liquid into medium bowl. Whisk 1/3 cup cooking liquid into dressing (reserve remaining cooking liquid for another use). Cook scallops in large saucepan of boiling salted water until just opaque in center, about 3 minutes. Using slotted spoon, add scallops to clams and mussels. Return water in saucepan to boil. Add shrimp and cook just until opaque in center, about 3 minutes. Drain. Transfer to bowl with shellfish. (Can be prepared 4 hours ahead and refrigerated.) Pour dressing over shellfish and toss to blend. Arrange slaw on very large platter. Mound salad in center and serve.