I just ordered two sided queen mattresses for my kids. They seem a bit firm, so I wanted to get something to soften them up. I also need a protective cover as both children occasionally bed wet. I think water resistant would be fine if not water proof. I am trying to come up with something that will not compromise the non-toxic value of the mattress since I bought them so my kids wouldn’t be exposed to toxins. So, I don’t want to just put a plastic cover on the mattresses. Is there something that would both offer some protection and added cushioning. The kids don’t mind the firmness, but I don’t think guests will be very comfortable when they sleep on the mattresses.
There is more about the pros and cons of different types of mattress protectors in post #89 here but if your kids occasionally wet the bed I would encourage you to consider a waterproof mattress protector or at the very least a thicker puddle pad that the retailer has confirmed shouldn’t soak through with an accident.
If you are looking for some additional softness then I would consider a topper that you can use for guests (perhaps latex or wool if you want more natural materials) but would still allow your kids to sleep on the firmer surface without the topper and I would buy a mattress protector that can be used over either the mattress by itself or with the mattress pad/topper.
Post #2 here and the topper guidelines it links to has more information and some of the better sources I’m aware of for choosing a topper.