I fly with a mini4 and works great.
Although I do have an inexpensive tablet holder, the min4 will fit in the arms of the remote if needed.
I'm a PC / Android user and purchased the mini4 just for flying the Spark as it seemed Apple products were working better with DJI software than the Droids when I purchased the Spark last year.
If you want to go full size iPad, it's been done and the use of a MavMounttablet holder is the preferred mounting system for larger, heavier tablets.
iPad Mini has a lot more screen real estate than the phone without adding much weight. Start out with an inexpensive mount (below) and you will have great view and keep access to the joysticks. I got mine for less than $20 and use it every flight (even with iPhone).
Tablet mount also gives better balance and feel compared to than jamming ipad into arms of remote.