Split is nice, brac (island) is more family orientated and lovely with some nice views/beaches/local caught fish etc hvar (island) is like the younger party island in that area. both are just off the coast of split and easy to get to.
dubrovnik is a little way from split but its a nice journey up the coast.
when we flew into split, we stayed down the coast to the west on the first night in Trogir, a small town with large and excsluive marina, so its kinda the posh out of the way area. it was very very nice.
if you head to split walk up the park/hill to the west of the main port section it has breathtaking views across the bay/town/ and out to sea over the islands. there is a nice little cafe for a drink and sandwich at the top with some comfy chairs to enjoy the view.