Just back from Dubrovnik. We did the 3 island trip from the Old Town. You don't really get much time at the first two, just a quick walk or maybe a cup of coffee. You have 3 hours on Lopud which has the only sandy beach around. It is called Sunj and you can take a golf buggy ride to it from the harbour and rent a sun lounger and umbrella. But it is very busy. The boat trip itself is very relaxing and the local scenery is stunning.