I would NOT go for original Ipad Mini, the Ipad Mini with Retina is far superior in performance. Checkout the Korg Gadget specs and you will see massive difference in performance between the two
In terms of performance
iPad Mini = Ipad 2
iPad Mini with Retina = iPad Air
iPad Mini 2 16GB WiFi only - iOS 8.2,
Apps - Cubasis, Korg iElectribe, Module and iMS-20, iSem, iProphet, iMini, iMPC Pro, DrumsLive, Yonac Magellan, Galileo and Tonestack, Animoog, Thor, ThumbJam, Gadget, Loopy HD, ReBirth, Audiobus, MidiBridge
Hardware - Akai LPK25, Nanopad 1 & 2, Nanokontrol 2, MS-20c (MS-20 USB controller from Legacy Collection), Beatstep, Blueboard + exp pedal, Novation Remote 25, Behringer ua202, Ubisoft Realtone, Alesis Trigger IO + Rockband3 Drumkit.