You should be able to delete photos copied onto the iPad via the CCK either via the trashcan icon in the top right corner if viewing the photo in full screen, or via the icon of the box with the arrow coming out of it (Edit button on iOS 6) in thumbnail view.
Your computer's iTunes can be used to add or remove photos synced from your computer. CCK photos (and those taken with the iPad) should appear in windows camera wizard or windows explorer on a PC, iPhoto, Aperture and Image Capture on a Mac.
CCK - Camera Connection Kit
The links below have instructions for deleting photos.
iOS and iPod: Syncing photos using iTunes
iPad Tip: How to Delete Photos from Your iPad in the Photos App
Another Way to Quickly Delete Photos from Your iPad (Mac Only)
How to Delete Photos from iPad
How to: Batch Delete Photos on the iPad
(With iOS 5.1, use 2 fingers)
How to Delete Photos from iCloud’s Photo Stream