I suppose you use the Camera Connection Kit to import them?
Make sure the videos are a compatible format:
If they are not, you'll have to import them to a computer to view them. Also, only files created on your camera are supported. If you copied the videos from somewhere else, or changed the name manually on the camera or SD card, the iPad will be unable to detect them.
Hi don,t know if it will help you but I now use RAVpower RP-WD01 which i purchased from amazon. It has a built in SD card slot and a USB connection built in wifi and can easy power a portable hard drive so you can copy the files from the SD card to the portable hard drive for back up or download to ipad.
I use it with canon EOS 600D and seagate portable hard drive for backup and ipad 4 128GB