Place cranberry juice and dried cranberries in a small pot and bring to a boil. Remove from heat and allow to cool. Stir in vinegar and Dijon mustard. Gradually whisk in olive oil so the mixture becomes a dressing. Season with salt and pepper, to taste. Rinse spinach and kale leaves and place in large bowl. Add vegetables, avocado and pumpkin seeds. Gently toss salad ingredients with the dressing and serve.