are dollars or euros used in the casino? I am guessing here, but would think it is Dollars.
is there a fee to cash travelers checks? There is no fee to cash
is there an ATM? Yes there is usually one in the Atrium and one in the casino. However, on at least two of our NCL cruises they did not work, so we just waited until we were in port and used an ATM at the local bank, with no issues.