#2, If you mean Cape Hatteras and the Outer Banks of NC, there is no super easy way to get there, but it is well worth the trip. Only two ways off and on the OBs. Hatteras KOA, Ocean Waves, Camp Hatteras are good bets for camping. OuterBanks
#3. While in Boston, there are some alternatives - Boston Minuteman in Littleton MA.. Normandy Farms in Foxboro.
On the trip west, with the time you have I would think you would want to take the MA Pike and NY Thruway. We live in central MA and when we go to Niagara area, we stay at the Villages at Turning Stone in Verona, NY. It is one of the nicest campgrounds we have visited. There a number of places around Niagara Falls - I personally like the options on the Canadian side a little better.
Have a great trip - you are going through some wonderful areas steeped in history and natural beauty.