In a very large bowl, toss together both types of Chex, Cheerios, pretzels, marshmallows, and candy. Using a microwave (in 30 second intervals, stirring after each one) or a double boiler, melt the white chocolate. Pour over the cereal mix, add a pinch of salt, and stir well to coat. It will seem like you don’t have enough chocolate to cover it all, but it will coat it all lightly. While stirring, add a few shakes of the nonpareils, as they will only stick while the chocolate is melted. Transfer the mixture onto a parchment lined baking sheet, sprinkle with a few more shakes of nonpareils, and leave to set. Break apart and store in airtight containers or bag up for sharing.