Well, thank you all for your quick and insightful replies.
I think I will order an Arduino Mega for development, even if the final application will use the Arduino nano.
While it arrives, I will try to use the NewSoftware serial port just for transmission to the iPad and see if it works.
By the way, Crossroads, just for information, iPad's serial port works at 3.3V, so I am using a voltage divider to talk to it and an op amp to boost it signals for the Arduino.
Thanks again.