Permitted recreation amenities may include playgrounds, tot lots, swimming pools, tennis courts and other such recreational facilities, which are solely for use by the residents of the cluster development. Recreational amenities shall not be limited to the foregoing so that the applicant may propose additional facilities. All such facilities shall be accessory to the residential cluster development. No advertising or commercial enterprise shall be permitted. In no case may such amenities occupy more than one-half acre of land or the equivalent of one acre of land for every 25 residential lots, whichever is greater.