@numan413 : Welcome to Karachi in advance. You have a very ambitious plan of spending 2.5 days with the family. OK, let me try and make a plan for you...a shopping mall is a shopping mall. If you want to catch a movie then Atrium is the place. But of you want to see the Dolmen mall and spend some money on shopping and at the food court then you cant get anything better than Dolman. Zainab market is a one of a kind shopping area and you need time to go over and hunt for what you want or just pick up something that catches your eye. No point in just browsing as then you will need a lot of time to just browse around without finding what you are looking for. And remember to bargain.
Port grand is a very nice place to spend some time and enjoy a light meal. Best time to go is just before magrib so you can see what it is like as the Karachi day turns in to the city of lights. I'm not sure of do darya and if you will get enough time to spend time and money there. Too many options of restaurants and food not always consistent.
My advise would be to hire/keep the cab (metro) for the day...dont hire a yellow or a yellow/back cab. You could also talk to your hotel rent a car for a day's outing.
Places to see: Quaid's mazaar, Flag staff house, Mohatta Palace, Sea View, Maritime museum, PAF museum, Port Grand.
Getting around Karachi could be a challenge depending which time of day and which direction you are headed for. Traffic is a major hurdle. What I suggest you do is; visit Quaid's mazaar, flag staff house, mohatta palace, Dolmen Mall and sea view on day one. and Maritime/PAF museum and Port Grand on day two. and zainab market on day 3 at 12 noon. No point going there earlier as the markets starts to open at around noon.
If you need more info, send me a PM. I will be glad to help. Best, k