Allenwood beach parking using HonkMobile app in advance

Hi All, planning to visit Allenwood beach on July 12 Sunday with my wife and kids (5 and 2 year old), really want to book parking in advance, i read about it and found i can use HonkMobile app to book parking spot but not sure how are they making sure that my spot is reserved since everywhere else on internet it says that Allenwood beach parking is first come first serve. Has anyone used HonkMobile to book spot at allenwood in advance and it worked for them?