I love this place. Holmdel Park is huge and has many trails to walk on. There are several playgrounds and they have a picnic pavillion that is available for reservation for your parties and reunions, etc....
There is a great little food kiosk with clean restrooms, and in the winter, after sledding down the huge hill, you can sip a cup of hot cocoa alongside the giant fireplace.
Longstreet Farms in Holmdel Park is awesome also. The animals are fun to see and they have many demonstrations during the spring and summer months for you to see how people lived in the 1800's.
Free admission and parking.