Croatia is one of my favorite countrys, I absolutly LOVE it. And if I could recomend something, I would say that croatias cost and its islands are the thing to see, relaxed, beautiful, and of curse some party to if that is on your agenda. my favorite islands are Hvar and Korcula
Dubrovnik its a real beauty too, but it can be a bit time comsuming getting there, no trains, only bus all the way on the costside, so its a nice ride. Maybe they have a airport to, but yes, as I said a bit time consuming, there is a lot els!