Good Icing Recipe please?

Hello. SO im maiking rice crispy treats from scratch for the forth of july. I want them to be kid friendly because the other deserts that are going to b offered at the cookout will not attract kids to them. So wheni mix in the marshmellows im going to combine red white and blue sprinkles in the mix. I would like to add some kind of glaze i have a ercream frosting recipe but my dad is really picky about using his powdered suger. So what else is another idea? I have alot of the jarred ducan hines frosting..if i heat it then pour it over do u think it would dry into like a glaze consistency? please help! give opions, advice and experiences