i did a bit of checking. A 6-quart Dutch oven weighs around 12-15 pounds (empty). Then, add what you are cooking. Also, I could not tell tell if the briquette or wood coals are included in that 25 pounds. The website does say "Car camping? Bring your cast iron and boil that pot of coffee at the same time, with room to spare.".
So, it is hard to say what would fit or work. You could ask them that question on their website.