If you plan to come and enjoy in Croatian Adriatic in the best possible way - sail around it. When you are booking your bareboat charter be aware of the fact that you need valid skipper's license to do it. (It should be valid in terms of Croatian legislation.) Possession of it is going to be checked upon your arrival for two reasons - to make sure it's valid for sailing in Croatian sea and to verify that you actually have it with you (didn't left it at home :-)).
Since, for sure, you do not want to come and then find out that your license is not valid check out list of all certificates issued by the competent authorities of all states that are recognized for operating Croatian flag boats and yachts.