For 5 days trip, your options are Kashmir, Swat and Kaghan.
Fairy Meadows needs more time as mentioned by Shahbaz and is not an easy trek at all. But at same time, i have seen families doing this trek.
In Swat, families can do the skiing slope climb in Malam Jabba. They can also do a little hike for Byun Village from Kalam main town.
In Kaghan, the most famous is Malika Parbat basecamp trek. It will be 5-6 hrs return journey if u plan to go on foot.
Explore the area beyond main Paye Meadows shops till Makra peak foot. Another option can be Manna Meadows trek which is 5 hrs return journey.
In Kashmir, Arang Kel trek is quite favourite these days. This one is also 5 hrs return journey. It starts from Kel town in Neelum Valley.