1- Dear Gaddani Beach Is near to Balochistan not in Karachi But you can go there easily & safely, we also went there for enjoy & Picnic this is a Beautiful Sea Side with Mountains, Only Private Transport available for this point from khi approx 2 hours drive from khi to gaddani & transporters charge 3 to 4 thousand for a day trip.
2- I think In a week you can not enjoy full Khi Include Gaddani Beach.
but you can visit some populer places like Seaview, Manora, Mazar_e_Qaid, Park Tower(shopping mall), Dolmin Mall, Jinah Terminal (Air Port), Port Grand (Food Street), Khadda Market Defence (Food Street).