N.J. Stat. Ann. § 40:61-4

The body in control of any playground or place of public resort and recreation of any municipality, in order to provide funds for improving, maintaining and policing thereof, may hold outdoor exhibitions, concerts, games and contests therein, and charge and collect reasonable admission fees for entrance thereto, while in use for any such purpose. No such playground or place of resort and recreation shall be so used on more than two days, nor more than eight hours in all, in any one week, and no admission fee shall be charged or collected from children under twelve years of age.