Hi! Wooden hides can be great, the only problem is that the mice will pee on them (and they are much harder to clean than plastic). The problem with putting something on the wood to protect it is that the mice might chew at it. I’m not sure if you would be able to find anything that is safe for them to ingest. In terms of wood untreated pine and cedar are unsafe due to their oils, along with a few other softwoods. I would stick with something like poplar which is commonly found. Some other options are birch, apple, or aspen. I’m not sure if you’ll be able to get those though.