hello, and welcome to the forum. i'm sure you'll get plenty of advice here to make your decision ! i think the idea of giving ebooks out at a conference is a brilliant one, definitely.
it might be helpful to have more information though. for example, when will this conference take place ? for such a large order, you should try to order early, to be sure there will be enough supply. and if you order a large enough quantity directly from the manufacturer, perhaps you could get a discount.
also, where will this conference be held ? to my knowledge, the wireless connexion could be a bit problematic. kindle has a wireless connexion, so if you could create a guide with links (like the MR kindle guide available
here) the attendees could simply download the latest version of the conference documents, however kindle might not be a very good option for other reasons. and i don't know whether it supports text formats like .doc.
another tip, pdf is not a good format for ebooks unless it is 1. formatted to the size of the screen, or 2. "reflowable". a better option would be .rtf (supported by several if not all devices) or html.
i am not sure whether other devices currently offer wireless connections, although i believe that will be coming soon on several of them.
don't hesitate to take a look around, you might find some useful info in some of the other forums ! you might want to start with the
wiki and the
comparison matrix.
please do keep us posted !