A lot depends on how you are traveling. For instance, if you are camping in NFS campsites cash is easier ($15 as some do not accept CCs as a form of payment), stopping for a snack and drink at a CS twice a day ($5), small meals (under $10, I pay cash). Most other stuff, i.e. larger meals, groceries, motels, RV parks, etc. I can use a CC however, sometimes I get a pretty good discount if paying in cash. You might consider stashing some cash in your bags, handlebars, etc. in case you lose your wallet.

have a great trip!