I usually stick to savory dipping sauces for sweet potato fries (think: sriracha aioli), but I think the tanginess of Greek yogurt would be totally delicious with a littlebit of honey, vanilla, and spices, like you suggest.
Little meatballs are like all the savory goodness of meatloaf wrapped in a bite - sized morsel; where each rugged crag offers a holding spot for sauce to hide.