Bill, I presume you bought red cedar. It will last a long time but white cedar lasts longer and has that nice gray.
If red cedar is outside in a sheltered area where it stays dry you can stain it or oil it for a great look. If it gets wet however the stain/oil keeps the moisture inside and grows black mould. You are better off to do nothing to it.
Whatever you make keep some 'spare' cedar for repairs as some pieces will fail while most are fine.
The price of cedar is shocking of late. I can buy good Ash for 1/3 the price of cedar!
As for Cetol, I'm only familiar with the marine grade. It could just be marketing. People have a love hate relationship with walking on sticky decks.