OK, so we went to Mauna Kea and we're back. Rented a 4WD from Harper Rentals (the only one that will rent 4WD that are permitted to go up to the top). We spent 45 min at the visitor center at 9000 ft. As we started to get back in the 4WD, I noticed my wife and kids put on really long faces. They were scared that something would happen to me if we went all the way up. I finally relented and U-turned back to the visitor center. I know, after all the preparation that went to it, I finally chickened out at the last minute. But the trip was not wasted by any means. We stayed for star gazing till 10 PM. It was so amazing. We had never seen so many stars shine so bright. The rangers were chock-full-of facts and had set up telescopes in the patio. They gave a laser-pointer guided constellation tour which was simply out of this world. Later I heard that the stars are not as clear even at the summit because human vision gets impaired at such low levels of oxygen at 14000 ft compared to 9000 feet. Made me feel much better.
If you get a chance to go there, don't miss the opportunity. Even regular cars can go to the 9000 feet visitor center. no need to rent a 4WD like I did. Beyond that, you need a 4WD. We saw a 2WD car all mangled up that was being towed back from the summit road. I heard that they can charge $1500-$2000 just to tow it back down.