Croatia, Split, Hvar and islands - advice needed!

Me and my friends are visiting Croatia, a day in Split and mainly going to be on Hvar for 4 days end of August Protected content tips on what to do, where to visit? We will have a hire car :)

What are the best clubs/ parties? Restaurants (local, and if you know of any vegetarian friendly restaurants, that would be really helpful. Interesting sights, places of interest etc. Can we actually join and get on a yacht for a day trip?

All advice and tips welcome :)