I think using a tablet for backup is problematical from the standpoint of economics and capacity. At 32 GB for $270 it is expensive and doesn't hold many pics, external drives are $100 for 3TB (100x the capacity and 3x less cost). If you are worried about durability get a small SSD (512GB) for the same money.
i use a 64gb thumbdrive for my storage, plenty of space for a week of pictures.
fyi, any pictures on the tablet when connected to wifi and you enable google plus will have all the pictures uploaded automatically. Just remember that we sometimes go to a country with minimal internet so you might hog the bandwidth.