Dubrovnik and Sibenik

How necessary is it to have Kuna in Dubrovnik and Sibenik? Is it possible to use credit cards or pay in Euros most of the time? How easy would it be to acquire some Kuna with in port if they really are needed. We would only need cash for bus or taxi rides, drinks and possibly entry to walk the walls in Dubrovnik. Any help0ful suggestions would be useful.

You can get Kuna from ATMs. Some places may take Euro but not all. It's more convenient to have some local currency.