Wood is naturally anti-bacterial, so bacteria generally does not sustain life for long and does not duplicate on wood like it can on plastic. If you want you can wipe down your toys on occasion. Never submerge your toys in water or allow them to be super wet for a long time though. Just use a damp cloth (not super wet), and a mild dish soap, use sparingly.
If the finish on your toy dulls over time you can simply fix it at home and give your toys a new look. Apply a 50/50 mixture of beeswax and any food grade oil such as mineral oil, coconut oil, or any other organic food grade oil. Simply wipe on, let it soak in, then wipe it off and you are done!
Just because a toy has lost some of it's shine over the years it doesn't make it unsafe, so it's totally ok if you don't re-apply a finish.