You can find a lot of good guest houses that are affordable for long term and get HUGE discounts if you tell them you plan on staying for more than a few days, bargain like hell and they will come down a lot. Some places even provide food etc. Restaurants are fine but I wouldnt suggest going out very often with random attacks still low chances you will be caught in one but Islamabad is a small city after all. Shopping all depends on what you want to buy