Adventure Club is quite popular and I believe they organize great trips. When I went to Fairy Meadows - I saw one large group arriving at FM organized by Adventure Club.
You can still join the trekkerz group and gain more information.
To reach fairy meadows starting from Islamabad - you will have to spend one night @ Chilas. Next morning a few hours drive to RaiKot Bridge. There you get the Jeep going up on a nice scary track up till Tatto village. Then hike for 2-3 hours.
This last hike bit is tough - especially with family. You can hire a horse from Tattoo to make it a little easier.