For this recipe, I suggest using dry roasted salted peanuts.  Dry roasted is a must because any extra moisture in the nut can affect the chocolate coating.  Having that saltiness is one of the best things about these clusters, as it is a nice contrast to the sweetness of the chocolate.  I've also made these with unsalted peanuts; sprinkle coarse sea salt over the clusters at the same time you add the sprinkles.