Waleed, what sort of 4x4 you are referring to? i went in a prado TZ, however, its not recommended to take it up to lake saif ul malook due to its size. Local willy's jeep is ideal for it.
I suggest, you visit Lalazar, Lake Lulu sar and Babu sir pass and if you are little more adventurous and up for trekking, lake dudi patsar is also a good place to visit, though i won't recommend it with family. Stop by at shogran and visit Siri Paya.
There are few other places like Sharan, Searl Lake, Ansoo lake but not at all recommended with family.