This dough is excellent with any of the mix-ins listed; experiment to find your favorite.
Place dough on a lightly floured work surface; sprinkle with nuts, chocolate, or fennel seed. Gently knead to incorporate. Transfer to an oiled bowl, cover with plastic wrap, and let rest 1 hour.
Divide dough into 8 equal pieces. On a lightly floured work surface, roll each piece into an 18-inch-long rope. To shape dough into pretzels, form each dough rope into a U-shape and twist ends twice. Fold twisted end down and pinch to secure. Transfer pretzels to an oiled baking sheet and let rest 20 minutes.
Preheat oven to 475 degrees. Bring a large pot of water to a boil; add baking soda. In batches, boil pretzels until puffed and slightly shiny, about 1 minute. With a slotted spoon, transfer to a wire rack to drain. Return pretzels to baking sheet; sprinkle with sugar. Bake until golden brown and cooked through, 10 to 15 minutes, rotating sheet halfway through. Serve warm or at room temperature.
Get the kids involved in the process -- forming the twisty shape is a fun activity for little helpers.