use the longer cable on your mbp and that will stop any tingling sensations,I'm using my mbp on charge right now and theres nothing.If you are getting shocked just by touching the case when it's charging, the Ipad needs to be returned ASAP. That is a safety issue and should not happen at all.
really? that's not normal? I got shocked a couple of times by a macbook pro, it's out of warranty, maybe i should take it in to see what they say.