1) Check your local museums. Go to the websites and look at their upcoming events as well as their normal exhibits. They might have a Spanish exhibit you can check out. Before you take your class you might want to visit it yourself just to make sure it is what you are expecting.
If you are in the bay area, CA you might check out the exhibit on the Arts of the Missions of Northern New Spain,1600-1821. This exhibit will be at the Oakland museum from February 26, 2011 - May 29, 2011. This is a really great museum by the way. I just went for the first time a couple weeks ago and was very impressed. The exhibit is called "Splendors of Faith/ Scars of Conquest." Find out more here.
2) If you can take just one class of up to 25 students consider taking them to a Mexican restaurant. Call or visit in advance. Check to make sure the waiter/waitresses will speak to them only in Spanish. When I did this with my classes. I would photocopy their menu. (I used their take-out menu) I had my students order with me in advance, everything that they would be ordering, drinks, etc. Then I had them figure out the total of their order. I helped them figure out the tax and the tip. They then had to pay me in advance to make sure no one "forgot" their money. I also had them practice how to order in Spanish with a partner and act out various things they might need to do and say a day or so before we went.