Eaten by lions I would think. Once they've done their bite to your neck you know about anything else. Being burned alive has got to be the worst way to go. Ever. I've had nightmares about that for years.
I'd take my chance with the lions. They would keep their distance from the fire, but if they had been fed recently, they wouldn't be interested in killing as basically they are lazy.
This whole story has been so exaggerated. The lions would not have come anywhere near the car, and obviously didnt as the family escaped unharmed and so unshaken that they could then sell this non story to the tabloids immediately.