My wife and I were in Pismo for several days with our son and a friend. After having a great day on ATV's rented from Arnie's (Sun Buggie does not rent to minors), we decided to give the dune buggies rented by Sun Buggie a try. While we did not need to be sold on trying the buggies, we listened to the whole story at the desk of Sun Buggie as to how safe the buggies were compared to the ATV's, especially for kids.
As an aside, it was clear to me that the ATV's could be very hazardous as the dunes could have very steep and tall faces. However, our 13 year old boys did great under constant adult supervision. It was a blast and we had an injury free day.
The buggie, on the other hand, was ungodly uncomfortable and very hard on everyone's spine given the thinly padded seats. It was very easy to get in stuck in the stand, even on gentle slopes, it felt very underpowered relative to the ATVs. Getting it unstuck was quite a chore (I am pretty strong and I still injured by back trying to pull it around to face downhill).
The company offers no refunds for any reason. We paid over $400 for 2 hours of use and returned the buggie after only 1/2. While I would return and rent an ATV anytime, I will never rent one of these dune buggies again. I could have just as well flushed the money down the toilet.