Either iPad Mini or iPad Air would work fine for P3A - for the Air you may want to upgrade the bracket which holds the tablet mount onto the transmitter to the metal/inspire version.
You can buy the official DJI part, or get a much cheaper version on ebay, it just screws on instead of the original plastic bracket, the pic below shows the original plastic bracket on left, metal version on right which is much less 'bouncy' (the tablet mount clip part is the same for both, its only the bracket onto the remote which is different).