Each beach and park has it's own set of rules. This type of setting is usually run by an individual city or a Parks and Recreation Department. You will need to check with them regarding their rules. Number of guests who will comfortably fit into this area. Parking at the beach is one of the greatest challenges.
Some locations have their own lot.
You will need to prearrange with the parking company to pay in advance for your guest's parking fee. If there is not a private lot it is very chancy to expect that everyone will find a parking place when competing with the general public. If you have to use street parking it will probably be metered. Give each guest a sign to place in their window and then assign someone to ride around on a bicycle and put in quarters at the appropriate time. The best option is to arrange for a central area where everyone will park.