Trekking via Seruni to the viewpoint Mt. King Kong takes you about 2 hours one way. Take a local guide in case you wish to start at night, as the road is small and bordered by high grass. During the day, you won't need a guide.
As hiring a Jeep costs you around IDR 450.000 to 650.000 - depending on the season - hiking to Mt. King Kong might be a refreshing alternative. It takes 2 hours walking to get from Seruni to Mt. King Kong. Although hiring a local guide will cost you some Indonesian Rupees as well, around IDR 200,000, it is cheaper than hiring a Jeep.
Besides, Mt. King Kong is not that crowded (yet) ass Mt. Penanjakan, thus no people standing in front of your camera. At Mt. King Kong you can find one spot very suitable to see the sunrise. Then, walk a few meters and your view will change to see the beautiful Mt. Bromo and the stunning Mt. Semeru behind it. As the sun is rising in the east while Mt. Bromo is situated south when standing at any viewpoint north of Mt. Bromo, having 2 spots to see both the sunrise and the color changing pallet when looking at Mt. Bromo is an advantage.
See you at Mt. King Kong.