@asifraja1 as you have 3 days for roundtrip and also require time to hike to ratti gali lake so i would recommend you to go via main road. Because you can cover more kilometers if you go via murree express way.
Day first: if you start travel early you can reach muzzafarabad easily. Take rest all night.
Day 2: start early again and i think you would be able to visit ratti gali and come back till evening. Stay there at doarian for night.
3rd day: start early back ride till lahore through main highways.