I would say that you definitely want to take the northern route in the summer and as for the dog, I guess it depends on how well he tolerates long days in the car? I've done the exact drive with my dog 20 years ago and it was easy...the dog never complained and he was great company. Obviously, you need to stop once in a while and let him get some exercise and have a peaceful meal but you will need the same so it works great.
