Vegetable Sushi Rolls for All Ages

Name: Vegetable Sushi Rolls for All Ages
Ingredients: 1/3 cup seasoned rice vinegar; 2 teaspoons sugar; 1 teaspoon salt; 1 1/2 cups short-grained sushi rice; 1 1/2 cups water; 4 sheets toasted nori; 1 kirby cucumber or 1/2 regular cucumber, seeded and cut into matchsticks; 1 carrot, cut into matchsticks; 1 small yellow bell pepper, stemmed, seeded and cut into matchsticks; 4 scallions, trimmed and cut into matchsticks; 1 (4-inch) piece daikon, peeled, and cut into matchsticks (or pickled daikon or 6 red radishes); 1/2 firm-ripe Hass avocado, peeled, thinly sliced lengthwise, sprinkled with lemon juice; Soy sauce