Can anyone recommend a one or two day boat trip to the islands out of Dubrovnik?
You can take a ferry to any of the islands from Dubrovnik. See schedules on krilo, jadrolinija websites
There’s a hatful of outfits that run day excursions to the Elaphite Islands out of the old port. They’re all basically the same itineraries with slightly varying prices and vessels. You can generally book these day of or day before. Head down there and see what suits you. Getting the sales pitch was part of the fun.