Okieee...... with family would be a different situation. If your family is also a nature lover then its OK otherwise there is no attraction or activity for families there. It is courageous of you and your family to decide about Kumrat.
Its not trekking.... its hiking all the way up till Jazbanda and then to Jazdand lake. Its 12 KM hike till Jazbanda from Jandrai and then further 06 KM trek+hike till Jazdand lake from Jazbanda. So total 36 KM treking+hiking involved in 02 days.You can well imagine the energy and fitness required for that.
The University Guest House is property of the Benazir Bhutto Shaheed University,Shreangle. You can book the Guest House rooms by contacting their office in Shreangle. The rate per room per night is Rs.4000. But the facilities they are providing is worth it.
If in case, The Guest House is full which is a norm as that is the Only Good facility there and they rent it out to VIPs only due to very limited 04 rooms only, you can opt for Forest rest house which is booked from Forest Department but as far as I know, that is being taken over by Pak Army as their Camp Office.
Third option is the Camps in Jungle. They provide capms, matresses and blankets.
As you are planning with family, so my dear, your priority should be the comfort of your family.