a two week wonder of the east coast sounds perfect for you! come up spend 3 nights at Timberlane Campground, it is the closest campground the Philly. I say 3 nights because you pull in in the afternoon, the next day you go to Philly, back to cg, second day in philly, back to cg, then the next day you leave. or you stay another day and explore the Camden waterfront including the Camden Aquarium and the USS New Jersey. Now you are off Liberty Harbor RV Park or the Newburgh, NY KOA. There are other threads on the pros/cons of these campgrounds. 3 nights again to spend 2 days in NYC. Now you are off across northern NJ into PA. You can either go right to Hershey (stay at the Hershey campground, it is worth it...shuttle to the park, discount tickets for the park), or stop at one of the many NJ and PA state parks for a relaxing night, depending what your preferences are. Hershey park/zoo/factory/town/outlets will be at least 3 days. From Hershey you are less then an hour from the Lancaster County, another great PA tourist area. Easily 3 more days can be spent in this area. From hear you can drop down to Gettysburg, PA for a couple days. How much more time do you have, and what else are you interested in. So much more to see between here and home. :)
We tend to plan trips that we spend 3-4 nights in a spot and move on. Occasionally we will spend 5 nights if the location has enough to keep us busy for 6 days. We leave in a week for 11 nights, and will be in WV, VA, and MD before we head back home. For us it is all about what we want to see, and what else we can see between the points.