What should I do for my reception?

I'm on a really tight budget because my fiance just got laid off for the next 5 weeks and I've already bought our cruise tickets. We're just getting married at the courthouse, so I wasn't planning on having anything big for the reception anyway, just a potluck at the park. That'll take away the cost of catering and reserving a building. But I'm concerned about the entertainment. Should I do a speech? Not everyone is going to know everyone else? Should I do seating arrangements? Should I have a set time? I want it to be low key and fun, but I don't want it to be boring w/ a bunch of people milling around.