Persevere, Penji. If they want the sweet snacks badly enough they'll come around to good home made alternatives and, when their taste buds adapt to the home made treats they will not crave the additives in the commercial cr**. You will have to be strong when you are shopping with them, though, and not let them talk you into buying the sweets off the shelves (and especially those placed at child height whilst you wait at the check out)