Fodor's Travel Talk Forums - Help for Road Trip w/17 year old son

I am at the beginning phase of planning a road trip in June for me and my son and I need suggestions. He graduates next year and is going into the Air Force, so this is our last excursion before he starts his own life. Our starting point is Pennsylvania and I would like to go to St. Louis to go up the Gateway Arch, stop in Kansas so he can visit his grandmother he hasn't seen in years, go up Pikes Peak, see the Grand Canyon, Hoover Dam, Yosemite National Park. My question is do we rent a car and drive out and then fly back or fly out and drive back. I have 2 weeks. My itinerary is very flexible. I just want to make this a memorable trip and my budget is on the low side. The key is making memories not luxuries. I am open to all ideas and suggestions. Thank you for taking the time to read this and assist me!!