Is it possible to pre-install apps on an iPad?
Contact your local Apple Store and ask to speak to one of their Business Consultants (each store has one.)  If you are buying bulk quantities of iPods Apple used to offer digital etching of your company logo on the back as well as the ability to preload it with promotional content (e.g. videos), I am not sure if they are doing this with Apps on the iPad but it is worth a shot and the Business Consultant is the person who would know or have the resources to find out.