Honestly trying to run a pirate themed event for more than a few weekends, isn't going to work.
I'm not trying to discourage you, but perhaps you haven't quite looked at all the angles of it.
1. Vendors who are you're biggest need, won't do it unless the restrictions are very light, and then you are not guaranteed vendors. Most travel from event to event so it would be hard to keep a good amount of vendors around for any length of time. This includes food vendors whom I know travel a lot.
2. Politics - They are everywhere, no escaping it. The worst thing you can do is become an enemy to yourself besides others. If you start acting like everything must be done your way, people will walk away. Asking people to be strictly 'period' isn't going to work either, you must be able to concede and be flexible.
3. Sponsors - This is a must especially when putting on large events. Also they are your greatest supplier of not just advertising, but to help defer certian costs.
4. Advertising - This is an absolute MUST! Not just a couple of small ads in the local paper, but a true and strong get the word out to all if you want people to attend.
5. Facilities- Finding a place (unless you own the property), is just half of the problem. You must have permits for this and that, it can take time to get them and then there might be some very strict restrictions such as no black powder, or people can only drink in a specified area, where porta potties will be (and how many) and on and on.
These are just a few of the many things to consider before putting on an event.