Our plan right now is to continue to head south in NJ all the way to Cape May, and take the ferry to Lewes, DE. Any advice you might have re how to get across the Susquehanna would be most welcome.
A couple of notes:
1. The ferry is a fun ride. Did a day trip from the GF's parents' house in Avalon to Rehobeth, DE using the ferry. Met a first cousin of Louis Garneau sailing down. Saw a school of dolphins swim under the boat on the way back. If you are planning to stay at Cape Henlopen State Park in Lewes, DE you will almost certainly need a reservation, at least on the weekends and probably during the week in high season. Weekends can be booked months in advance.
2. You probably know this, but the U.S. 9 draw bridge between Somers Point and Beesley Point is no more. The only ways to cross the Great Egg are to go pretty far inland or hug the coast. I recommend riding south through the shore towns (Ocean City, Strathmere, Sea Isle City, Avalon, Stone Harbor and the Wildwoods). The boardwalk in Wildwood is a sight, with it's amusement piers and carnival games. I would try to avoid the heart of Atlantic City. Not bike friendly at all. You may ride the boardwalk up to a certain time of day (maybe 10 or 11 a.m.) Taking that south until it ends in Ventnor and then hitting the street is the way to go.
3. If you won't be hugging the coast all the way to Cape May, there is a nice camping spot in Woodbine, NJ at Belleplain State Forest. It's large, but a reservation for weekends during the height of summer is probably a safe way to go. In fact, a reservation for any of the private campground along the U.S. corridor is probably advisable during the summer. I am pretty familiar with Atlantic and Cape May Counties. Feel free to send me a link to a map of your route in those areas and I will take a look at it.
4. If you want to ride across the Susq. you are stuck with either U.S. 1 across the Conowingo Dam or PA 372 much further up stream. The former is narrow, shoulderless and can have heavy traffic. Take a look at it on Google Maps Street View to see the conditions. The latter has a shoulder.