OpenGL 2.0 or 3.0 for newer iOS

Hello. I am releasing a game for iOS. I have tested the game on iPad Mini, iPad 3 / 4 iPhone 5 and the game runs well. Anyway i have send the game to a tester with iPad Air and he said that the game crashes constantly.. There are atlas textures which are 4k. I was wondering... If i target iOS 7.1 shoud i release with OpenGL 2.0 or 3.0? Or maybe i shoud leave it to Automatic?? If i release to 3.0 is the game going to run well on iPad 3, 4? Thanks