Apple's Camera Connection kit allows you to load photos from your camera to the iPad over USB, but you won't be able to snap photos and have them instantly appear on the iPad. For most DSLRs, the camera won't be able to shoot when it's in USB mode.
What you could do is use an app like teamviewer to hook your iPad up to your computer, and use software like Aperture on your Mac to set up a tethered shoot with your camera. You'll need to have that Mac wired to the camera (so it's not an idea solution if you want to be all wireless), and you'll need to have a wireless internet connection, but you'll achieve the goal of having a wireless iPad that can trigger a photo to be snapped and instantly get that photo full screen onto your iPad (at least show within the TeamViewer app on your iPad) where you can make adjustments.
If you needed an easy way to get those photos on the actual iPad for sharing, you could set up Aperture to automatically store the photos in a DropBox or Google Drive folder. Snap photos in TeamViewer through Aperture running on your Mac, then switch to the Dropbox app to download those photos and share.