We really enjoyed the trip up to the Hualalai volcano.
The military vehicle itself was a trip. It took us up "roads" that would seem impassable. Hikers on the side of the trail actually stood with their mouths wide open as we passed them.

We went right up to the edge of the throat of the volcano, and even rappelled down into a lava tube!
It sounded too challenging at first, but there were options to not do that part. However our guide was so great that two children, one 70-year old lady, and three of us other middle-aged adults did fine. My wife said she felt like she was on "Survivor" or "Amazing Race."

The guide filled us in on Hawaiian history & lore. He pointed out plants and geology. At the highest elevation we had several varieties of great local breads, juices and water.

The combination of the 4-wheel ride, the physical activity, information, sites, hike made for a unique experience that I highly recommend.