We're a family of 6 (children aged 24, 18, 15 and 12) planning a family vacation in the US. We don't have plane tickets yet but we're planning on flying to Chicago or New York on 17th July and coming back to Poland on 10th August from San Francisco or Phoenix. It'll be our first US trip together, some of us have been to the US before. As you see we'll be flying to the East Coast and coming back from West Coast. At first we wanted to do a road trip across the US but there are so many places we want to visit we realised 3 weeks might not be enough time to do that so we decided to fly from East to West Coast. We have no experience in planning this kind of vacation. My question is: do you think it's better to buy multi-city plane ticket now or buy just round trip ticket and later buy plane ticket to fly from East to West Coast? Or maybe it would be cheaper to drive from East to West Coast?
I will appreciate your help!