My aircraft Group have found the I Pad mini II 16GB without phone card, just fine for aircraft use. (SkyDemon)
If you are going to use it for home use etc you may want more capacity for photos movies etc.
We use an external GPS receiver in the windscreen and have never had any signal problems. For longer flights a USB plug in the cigarette lighter socket takes care of in flight charging, but flights of 2/3 hours ok with fully charged device.
I would not dream of flying around our local area, SE around the London control area, without it for accurate navigation and situational awareness, dispite what the CAA map and stopwatch brigade might say!