End-Of-The-Season Band Party

I want to throw an "End of Marching Season" Band party for the members of my school marching band. The only problem with this is that my band consists of 180 members. I have about an acre of land behind my house, and the house itself is pretty large. Does anyone have any suggestions on how to throw this party without the sheer number of people bcoming a problem, as well as any ideas on how to make it memorable?