You can use virtually any finish you want, as all fil-forming finishes are non-toxic when fully cured or fully dried, depending on the finish type. What does fully cured vs fully dried mean?
Varnishes, polyurethanes (which is really a varnish), etc. are reactive finishes, which means that there is a true chemical reaction as and after the film is "dry". That's why most application instructions say something like "recoat within 2-4 hours or wait at least 24 hours." After a couple of hours the film is dry enough to handle, but it is not cured. This allows the next coat actually to bond with the previous coat. Ater a few hours that chemical bonding will not occur or will be very weak, so then you have to wait long enough for the film to dry/cure sufficiently to be scuff sanded without "balling up" and causing a whole range of problems. To be "fully cured" these finishes require up to a few weeks for the chemical reaction of curing to take place. Once fully cured, varnishes are "food safe," hence "baby safe."
Shellac and Lacquer are evaporative finishes, i.e. they dry with no chemical reaction. When an evaporative finish is completely dry it is also completely non-toxic. In fact, shellac is often used as the hard outside coating on candies and pills. The solvent is what causes problems.
If you want, email me and I'll give you some references.
I liked what I did then, but I like more what I do now.