Heat oven to 275°F. Line a baking sheet with parchment paper; set aside.
Mix together corn Chex, pretzels, peanuts, and Cheerios in a large bowl.
In a small sauce pan, combine butter (or coconut oil), honey, mustard powder and salt. Place over medium-low heat and stir until butter is melted and mixture is smooth. If using avocado oil you won't need to heat the mixture, just stir until everything is combined. Pour over pretzel mixture and stir until everything is well coated. Stir gently so you don't break up the Chex. Spread evenly on the prepared baking sheet. Bake for 1 hour, stirring every 15 minutes.
Remove from the oven, and sprinkle the Easter sprinkles over the mixture while it is still warm otherwise they won't stick. Toss the mixture every 10 minutes or so until it cools so it doesn't all clump together. The Chex mix will crisp up as it cools. Store in a ziplock bag or sealed container for up to 2 weeks at room temperature.