In a large bowl, combine the cereals, pepitas, pistachios, and pretzel sticks.
In a small bowl, stir together the remaining ingredients until well incorporated. Pour this mixture over the cereal mixture and toss well to coat but gently so as not to break the cereal and pretzels.
Spread the mixture out on a baking sheet in a single layer and bake for 45 minutes, stirring gently every 15 minutes. Remove the baking sheet from the oven, let the mixture cool, and serve, or store in an airtight container at room temperature for up to 2 weeks.