iMessage User "is not registered with iMessage"
Messages on an iPad can't send an SMS so you can't send a message to a non-Apple phone. You'll need an SMS apple like Google Voice for that.

There Shouldn't be any problem sending an SMS from Messages on the iPhone though.

I've never heard of a three month version of AppleCare but both the iPad Mini and iPhone 5 come with 90 days of free phone support and a year warranty so I don't know why Apple would want you to buy anything.