When we took our first trip to the family cottage 7 1/2 hours away in Canada our girls were almost 4 and 2 1/2. We had more adults in the car than you did, but most of the things I did with them you could do alone. I packed an activity bag for each of them - that they could easily get into by themselves. In it I had a few of their favorite toys, books, crayons and a small pad of paper to color on. I kept snacks & water bottles in the front seat with me, so that I could control how much they ate/drank at a given time. Our oldest was potty trained, so we didn't want her to get so much water that we had to stop every 30 minutes!! Even though our youngest wasn't potty trained, every time we stopped at a rest area or to use a restroom, we all got out of the car to stretch our legs and let the girls run a little bit. We didn't stop at every one, but we stopped often enough. Because you are alone, I would put the snacks on the front seat where you can easily get them. Also, if your son isn't normally in the center of the back seat, I would move him there for the trip just so that you can reach him easily. You may find that he sleeps more, possibly in shorter periods of time, but I wouldn't count on it - we left in the late afternoon that first time hoping they would spend the first couple of hours taking a nap, we were about 5 hours into the trip when they finally fell asleep for 30 minutes!! We've talked about getting the portable DVD player for the girls, but have managed to do the trip 2 times (going on 3) without it and haven't had a problem.