Put the potatoes in a large pot and cover with cool water. Bring to a boil and cook until tender, 12 to 15 minutes. Drain and transfer to a large bowl.
In a separate bowl, combine the mayonnaise, mustard, sugar, salt, pepper, eggs, scallions, celery, shallots and lemon juice; stir to mix together. Add the mixture to the potatoes while still hot, mixing until the potatoes are coated. Transfer to a serving bowl.