I always leave Islamabad at around 8 am and stay at Panno Aaqil. I personally wont reccomend to such a long drive where you cover the easy path at the start and will cover the trickiest part (from Sukkur till Hyderabad) afterwards when you have exhausted. So i personally advise you to stay at Sukkur. There you found some good hotels with in the range of 3000 to 5000. and left sukkur in the morning at around 8 am next day..
Remember, you have to fill up the tank at Islamabad then again fill up at Sial Motorway Rest Area. After that you can easily go uptill Multan Sukkur Motorway there you found the petrol pump at first stop after the Start of M5.
Hope this will help you out.