Hi
I am currently using iPad 3 mini 16gb and it is working perfectly. You may also want to get a 250mm long usb to lightening cable (90 degree connection at both ends).
I found with the iPad 3 mini and the 250mm cable is the best setup for me. You can also record the iPad screen during flight using the iPad record function.
You can get a good second hand iPad mini 3 for around a £100 and the cable for about £2 to £3 each.