Whenever I run into a request for cooking for allot of people, I think it's totally fair to make a list of questions, sit the owners down and ask them all. You can learn allot about them, and how it is to work with them by the way they respond. If they are impatient or dismissive, you can get a hint of how they will be when you are working for them. I would not price the job until after your discussion. If they are hard to work with, it may not be worth it at any price. If they are cool, quote your expenses plus what you think is fair with the hopes that they will call you back next time.