Are you sure they don't just want a nice interesting dinner? They had said they want it prison themed? I'd make sure.
I had a friend who was a guard at a large prison. Make sure that this is something they would want.
I would make a nice little picnic to pick at for hours while watching festivities on TV.
Best charcuterie I could afford
and if I felt like cooking I'd make a Pissaladière. If you haven't tried this before it's simple to put together, but really depends on the best anchovy in olive oil and the best olives. I use a puff pastry, not pie dough or pizza dough which could also be used. Even if you think you don't like anchovy this will convert you.
Here's the recipe I use http://www.trinigourmet.com/index.php...