Thank you very much. I was thinking about PETG but I was skeptic about its total non-toxicity.
Generally most plastics are non-toxic at room temperature (i.e., not when burning or melting). PET for instance is what plastic most disposable plastic water bottles are made from, and while it's not the same thing as PETG, it's very similar. Plastics are mostly inert in their fully cured solid form. All of the common 3d printer filmanets are non-toxic at least for the base resin.
A few issues come up: first is that few filament manufacturers will tell you what else is in their filament. There are dyes and pigments, and also additives (like other plastics) to modify the melting and extruding properties. Most of it is innocuous, but it's good to get confirmation on the specific filaments you are going to use.
Some filaments have fibers or powders in them. Glass, carbon fiber, metal powders, stone powder and so on. I would avoid those in your case. Not that they are all automatically bad, it's just a whole extra level of concern -- especially if the parts might get cut or ground and produce dust.
Finally, while many of the plastic resins are food safe, 3D printed parts are generally *not* considered safe for food contact. The concern is the layer lines. These provide gaps and cracks where food can get stuck, and then bacteria can grow on the food. It's difficult or impossible to wash off. For toys that aren't going to contact food I don't think it's a big deal, but if you are targeting very young children or special needs children that might be excessively prone to putting stuff in their mouths, I would consider avoiding 3d printed parts or finding a more definitive answer than "internet randos".