Kusadasi offers a great beach, a nice marina with very good shops (clothes, shoes, carpets, nice souvenirs like the "boncuk" which brings luck). The traditional "karavanseray" is a must. You can also visit the castle, book a boat trip, enjoy ice creams or Turkish pancakes called "gozleme". Two days are enough in Kusadasi. I definitely recommend to visit the regio (Efes, Sirince, Selçuk, the national park Dilek). For the kids, you have also an aquapark called Adaland and a dolphinarium. In Kusadasi, everyone will find great activities ranging from shopping to cultural tourism.