One of the most important aspects of planning a public event - Pagan or otherwise -- is to make sure all the legal mumbo-jumbo is taken care of in advance. And that means NOT the day before, but well in advance. If you're in a park or other public setting, you need to find out ahead of time what the rules and regulations are as far as noise, bonfires, etc.
Some areas may have restrictions on whether or not you can permit vendors to come in and sell products or services at your event. Find out ahead of time - you don't want to be notified the morning of your celebration that all those Tarot readers have to have a state business license on file, or that food servers need to be registered with the county Health Department.