Hi, and welcome to the forum!
Some thoughts:
1. Do you use speakers in both rooms at the same time? If not, then you could consider getting a speaker switch box and running all of the speakers off of the main outputs. With that, you could run room calibration separately for each room (if your receiver supports multiple settings, and I'm not sure if the RX-A820 does), and you could use any input for the second room that you can use in the main room.
2. If cost isn't an issue, have you considered having two receivers - one for each room? That way, I know that you could do room calibration in each room, and running the receivers might be more intuitive to family and guests because they would be right there in the room with them. That does, of course, depend on the sources that you want to use. So far, you've mentioned playing music over Apple devices, and you can distribute those wirelessly between rooms.
3. An Airport Express would allow you to connect to your Apple devices and output either a stereo analog signal or a digital optical signal, and you could connect it in the second room to either an amplifier (so, no room calibration) or a second receiver.
Just some thoughts. There are others here that have whole house audio distribution systems, and they might have some good insight for you.