Michigan has the five Great Lakes and numerous smaller beaches. You can camp or stay in a motel. Port Huron is one place to check out.
Drive to Dearborn, near Detroit, and spend the day at Greenfield Village, a historic village with the Henry Ford Museum (cars and planes) next to it. The village has Thomas Edison's place, the Wright Brothers' bicycle shop, a glassblower's shop, that kind of thing.
Or come to central Pennsylvania. See Gettysburg, see Hershey. Hershey has the chocolate museum, etc, but it also has an amusement park, botanical gardens, and a LQS. Hotels are expensive, but you can stay a bit outside for much less.