Even if you decide to go with cedar for shelving, Don't get green cedar (if you can find it) because it will have way too high a moisture content and will check/crack as it cures. KD will be much drier than you will need (usually around 10-15% moisture content) whereas air dried will be somewhere around 20%. Most all will be KD, which is why you have to let the wood aclimate to the moisture content of the cooler, just like priming a regular humi. I've got a cedar shelf in my cooler, but only because I had a fairly large piece of spanish cedar in the wood pile. The wire shelving would be much easier and more efficient for air circulation.