A. Michael Dresdner: "As a rule, babies are more hazardous to finishes than finishes are to babies. For practical purposes, virtually all common, clear film finishes are safe once they are dry. However, if you are particularly concerned, go with a shellac finish. The majority of shellac sold in the world is used for coating fruit, candy, and medicine. It is completely edible, yet makes a beautiful, fast drying, easy-to-apply finish. Another advantage is that even in its liquid form, the only solvent it contains is alcohol. Since it is entirely made by bugs and not synthesized by humans, I assume it meets your "natural finish" requirement also."