Try pop those dents out! You can make them look a lot better, use a fist and knock around the dent in the high areas. I worked at a car lot and did it all the time. You may be able to get at the bumper from underneath. Popping out dents to make it presentable is not that hard, the metal wants to go back to its original shape. These dents often go right out. I would keep the details down in the add, make it shorter. You can tell them the bad stuff and why it's not such a big deal on the phone or in person, it's better then in text as you can explain it to them and answer their questions on the spot.
Think of the Craigslist add like a resume, its purpose is to get you the interview, calls, lookers. You do the selling on the phone or in person