Simple answer? Mr Microphone! that's right kids, tons-o-fun. As seen on TV! Order now and we'll throw in a garish orange windscreen!!
seriously,though, It is a low power wireless mic that that transmits on the FM frequencies. Depending on how large the exhibit is, you can just use small pocket AM/FM radios or 'toy' style boomboxes in the outlying buildings. If you can post pics, along with an idea of the area to be covered(size) I can give you a informed recommendation. Working with museums in the past, I know that there are/is never enough budget dollars. With a better idea of what you have to work with, I think I can help you get the most bang for your buck. I am an Systems Engineer for live event productions co's all of which use wireless mics often. even if Mr Mic isn't suitable for your project, as someone on here says: There are many ways to get to Rome. "Data, I need more Data!" Capt. Picard speaking to an Android.