High Point State Park New Jersey
My favorite place to visit in New Jersey is High Point State Park (http://www.state.nj.us/dep/parksandforests/parks/highpoint.html). It is a beautiful, pristine park, with lots of family-friendly attractions.
You can camp there, or you can also rent cabins to stay in. When I went there with my family, we stayed in a cabin. You can go swimming at Lake Marcia, where there is a lifeguard present to ensure safety for your kids. You can also climb the High Point Monument, a monument to all war veterans.
If you climb the monument, you can see out very far into the distance, to both the Catskills Mountains and the Pocono Mountains. High Point State Park is in the Delaware Water Gap, and the beautiful Delaware River runs through it.
The Appalachian National Scenic Trail also runs through the Park. Hiking a short distance on the Appalachian Trail with your kids is a great way to spend a day while staying at the park. You can teach them the history of the trail while you hike, and you are likely to run into friendly thru-hikers who are trekking the whole length of the trail, from Georgia to Maine, all 2,181 miles of it!
If you want to teach your kids how to fish, you can also go fishing during your stay at High Point State Park. When my family went fishing there, we caught a trout! We were told that there are also many large mouth bass swimming around in the rivers, lakes and streams at the park.