Where to RV on East Coast

The Pocono Mt. REgion of Pa might be interesting to you. I know one large CG, Otter Lake CG in the Stroudsburg area is literally on a huge lake with swimming, fishing, etc. available. There are other options as well. The Northwest region of NJ is also possible, with lakefront Campgrounds in the area as well. Might want to check out the Lancaster County, Pa region too. The area has numerous campgrounds, unique communities and attractions (it "Amish Country", and Hershey Park is nearby). None of those areas is very far from you at all, I don't think. You can look at https://www.campgroundreviews.com/ for info on campgrounds and descriptions so you might find something enjoyable. I would agree with others who suggest not going too far from home. Sounds like this will be a 'first time' adventure for the family and it may turn out to be too different for some! Also suggest you take notes, literally, when given instructions when renting the RV, and absolutely don't hesitate to seek help when you set up or take down the rig at the CG! Campers are generally very helpful people!