There will be no issue.We have toured last year in July upto Khunjrab. But avoid to go back through Babusar Pass .It is little difficult,as the road's angles are little high.
KKH's contouring is fine enough.and not more than 20 to 25 degrees at any place.
Chilas -Babusar-Naran Balakot Mansehra route is an enjoyment. Mansehra naran Chilas is enjoying but contouring more than 45' degrees at some peaks. Chilas Naran Mansehra 's contouring is more than 50' degrees before babusar.