Measure cereal into a very large bowl and set it aside.
Make coating. In a microwavable bowl, microwave chocolate chips, peanut butter, and butter for 90 seconds, stirring halfway through. Pour mixture over cereal, stirring well until evenly coated.
Measure powdered sugar into a very large (2 gallon or larger) plastic bag and shake until well coated. Spread on waxed paper to cool.
Add dried strawberries, M&Ms, and marshmallows to coated cereal and shake again. Serve in a clean bowl or directly out of the bag.
Notes
Don't have a 2-gallon bag? Just split the cereal roughly in half for the shaking portion.