I know you said you've decided to drive but I want to add there have been Amtrak specials for kids visiting colleges that might make the train much cheaper than you think. http://www.campusvisit.com/amtrak/

If you do decide to drive, time your exit and entrance into the cities to avoid rush hours. Don't bother with valet parking but find a garage near the hotel using either bestparking.com or iconparking.com which allows you to reserve in advance and guarantees price if you print the confirmation and have it with you.