the top of the Chesapeake!
The North East River (North East, MD) is right at the top of the Chesapeake - with traffic about an hour and ten minutes from King of Prussia and often quicker.
Once on the bay there is good sailing, plenty of places to anchor out for the night, weekend or longer. The top of the bay more fresh than salt water which I suspect is easier on the gear and more pleasant for the kids to jump off and swim - no stinging nettles up this far.
Mooring is very reasonable, services and restaurants are usually close by.
What I enjoy most is having multiple destinations surrounding the area - I can daysail to beaches near Turkey Point, tie up for lunch near Charlestown, overnight on the Sassafras, Worton Creek, Still Pond, or sail to Rock Hall or Annapolis.