Getting around Lombok, Indonesia

What is the best way to explore Lombok? We plan to do the Gilis then move to the Rinjani National Park, then to Mandalika.

On the Gilis, transport is not needed for us since we can either walk or take a bike. But of course going around the mainland require a proper transport.

Scooter is definitely not for us since none of us can ride a scooter. Private driver is an option, but not the cheapest. We're thinking to rent a car and drive around the island by ourselves. Would it be recommended? How does the traffic there look like, as well as the road and the terrain (wide/narrow roads, steep or flat, etc)?

Thanks for the insight!