Putting iPads out publicly always invites security issues of them getting stolen. The situations I have done are where a Surveyor gives a client an iPad to answer questions while in the presence of the Surveyor.
iPads work great with AirPlay. Just get an AppleTV ($99) and you can show your iPad up on a TV connected to the AppleTV. Works great. But if you want to get complicated, I have done web services where FileMaker sent an RSS feed to a big sign on the side of a building to display information from the database. But I don't think that is what you are looking for. Remember that the AirPlay just duplicates what is on your iPad's screen. Your situatoin may want a separate device feeding the screen with results coming from multiple iPads or something like that. There are all kinds of things you can do with some creativity.
Not exactly the same, but Tim Cimbura (wish there was a way to "tag" people here, like on Facebook) made a solution for the MN State Fair's animal judging. Here's a link talking about the solution:
Pretty cool stuff. And this was 2 years ago, with FM 11 and the original FMGo.
Like I said, not exactly the same use case, but I can see it being a similar setup. Your survey participants are the "judges" in this case.
I did a lot of research for securely mounting iPads and also on plugin alarms systems.
Frankly there are many fewer solutions than I expected and most of them rely on someone being close.
All of the manufacturers who I approached were happy to consider custom jobs.
I am doing a quote at the moment for a community access project. My numbers say it is cheaper to replace the stolen ones... depending on the honesty level in the community. Small towns are pretty safe unless someone has a grudge :-)