We are a family of 4 (two adults, two kids- 8 & 3) planning our first ever summer road trip. We are flexible about the time to travel- we are both teachers and have from the second week of June to mid August to travel. We are thinking that 2-3 weeks is good for our first try.
Our trip will start in the Greenville SC area and we are considering the following cities:
Richmond VA, Williamsburg VA, Washington DC, Port Republic NJ (visiting friends), Atlantic City NJ, Philadelphia PA, Hershey PA

What other suggestions do you have for us first timers? Where are some good off-the-beaten path stops? We can go further than PA, so are there any not to be missed spots not too far away from this area?