I recommend using whole milk Greek yogurt for a thicker and creamier texture. The runnier the yogurt, the thinner the frozen yogurt will be. You can use flavored yogurt for added sweetness, but if you are planning to share with your little one(s), I recommend avoiding added sugars as much as possible until 2 years of age. Even without it, the mixture will be plenty sweet for them with just ripe peaches and banana.