If you use ipad 2 resolution they still look okay to the untrained eye, iPad 2 should generally be fine - But the better the resolution is always the best.
It's pretty easy to just make your images twice the dimensions and scale the actors down. Using resolution independence will auto scale the actors and create crips images.
Comments
iPad 2 graphics on an iPad 3? No!
iPhone 3GS graphics on an iPad mini? No!
I could go on!