The iPad's own Notes app is fine for taking notes, and its Calendar app is perfectly suitable to manage your appointments. There are tons of alternative apps for both, but I don't see the point. There are two exceptions: The Notes Plus app ($4) lets you take handwritten notes with a stylus (such as Ten One Design's Pogo Stylus), then export them to PDF, though it doesn't convert the handwriting to text. You can also type in text and include audio recordings. If your notes include drawings, Notes Plus is the way to go. The Notability app ($5) is designed for people who take notes while recording lectures, presentations, and the like. Afterward, if you tap any text you entered, Notability will play back the audio recording from that point in time, so you can hear what was being said as you were typing.
Beyond these broadly useful utilities, chances are some workers will also need additional apps for more specialized tasks. So I've put together a collection of such additional business apps that you might make available to employees as part of an in-house catalog or point them to as recommendations.
Should you provide a keyboard and VGA connector? The iPad's on-screen keyboard is surprisingly easy to use, especially in landscape orientation, where it's a full-size keyboard. You don't get the tactile feedback of a key press, but I found I adjusted very quickly to touch tapping without that feedback.
Apple makes a very nice Bluetooth keyboard, the $69 Apple Wireless Keyboard; other Bluetooth keyboards work with the iPad as well. You would think they make typing faster, but they don't unless you're in stenographic mode, transcribing a meeting or call as opposed to writing and editing. The reason is that there are few keyboard shortcuts available for iPad apps, so you're constantly taking your hands off the keyboard and moving them to the iPad's screen. That kills any speed advantage of the physical keyboard.